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1.4.18.7: Major Oceanic Biomes - Biology


Learning Objectives

  • Compare and contrast the characteristics of the ocean zones

The ocean is the largest marine biome. It is a continuous body of salt water that is relatively uniform in chemical composition; it is a weak solution of mineral salts and decayed biological matter. Within the ocean, coral reefs are a second kind of marine biome. Estuaries, coastal areas where salt water and fresh water mix, form a third unique marine biome.

Ocean

The physical diversity of the ocean is a significant influence on plants, animals, and other organisms. The ocean is categorized into different zones based on how far light reaches into the water. Each zone has a distinct group of species adapted to the biotic and abiotic conditions particular to that zone.

The intertidal zone, which is the zone between high and low tide, is the oceanic region that is closest to land (Figure 1). Generally, most people think of this portion of the ocean as a sandy beach. In some cases, the intertidal zone is indeed a sandy beach, but it can also be rocky or muddy. The intertidal zone is an extremely variable environment because of tides. Organisms are exposed to air and sunlight at low tide and are underwater most of the time, especially during high tide. Therefore, living things that thrive in the intertidal zone are adapted to being dry for long periods of time. The shore of the intertidal zone is also repeatedly struck by waves, and the organisms found there are adapted to withstand damage from the pounding action of the waves (Figure 1). The exoskeletons of shoreline crustaceans (such as the shore crab, Carcinus maenas) are tough and protect them from desiccation (drying out) and wave damage. Another consequence of the pounding waves is that few algae and plants establish themselves in the constantly moving rocks, sand, or mud.

The neritic zone extends from the intertidal zone to depths of about 200 m (or 650 ft) at the edge of the continental shelf. Since light can penetrate this depth, photosynthesis can occur in the neritic zone. The water here contains silt and is well-oxygenated, low in pressure, and stable in temperature. Phytoplankton and floating Sargassum (a type of free-floating marine seaweed) provide a habitat for some sea life found in the neritic zone. Zooplankton, protists, small fishes, and shrimp are found in the neritic zone and are the base of the food chain for most of the world’s fisheries.

Beyond the neritic zone is the open ocean area known as the oceanic zone. Within the oceanic zone there is thermal stratification where warm and cold waters mix because of ocean currents. Abundant plankton serve as the base of the food chain for larger animals such as whales and dolphins. Nutrients are scarce and this is a relatively less productive part of the marine biome. When photosynthetic organisms and the protists and animals that feed on them die, their bodies fall to the bottom of the ocean where they remain; unlike freshwater lakes, the open ocean lacks a process for bringing the organic nutrients back up to the surface. The majority of organisms in the aphotic zone include sea cucumbers (phylum Echinodermata) and other organisms that survive on the nutrients contained in the dead bodies of organisms in the photic zone.

Beneath the pelagic zone is the benthic realm, the deepwater region beyond the continental shelf. The bottom of the benthic realm is comprised of sand, silt, and dead organisms. Temperature decreases, remaining above freezing, as water depth increases. This is a nutrient-rich portion of the ocean because of the dead organisms that fall from the upper layers of the ocean. Because of this high level of nutrients, a diversity of fungi, sponges, sea anemones, marine worms, sea stars, fishes, and bacteria exist.

The deepest part of the ocean is the abyssal zone, which is at depths of 4000 m or greater. The abyssal zone is very cold and has very high pressure, high oxygen content, and low nutrient content. There are a variety of invertebrates and fishes found in this zone, but the abyssal zone does not have plants because of the lack of light. Hydrothermal vents are found primarily in the abyssal zone; chemosynthetic bacteria utilize the hydrogen sulfide and other minerals emitted from the vents. These chemosynthetic bacteria use the hydrogen sulfide as an energy source and serve as the base of the food chain found in the abyssal zone.

Coral Reefs

Coral reefs are ocean ridges formed by marine invertebrates living in warm shallow waters within the photic zone of the ocean. They are found within 30˚ north and south of the equator. The Great Barrier Reef is a well-known reef system located several miles off the northeastern coast of Australia. Other coral reef systems are fringing islands, which are directly adjacent to land, or atolls, which are circular reef systems surrounding a former landmass that is now underwater. The coral organisms (members of phylum Cnidaria) are colonies of saltwater polyps that secrete a calcium carbonate skeleton. These calcium-rich skeletons slowly accumulate, forming the underwater reef.

Corals found in shallower waters (at a depth of approximately 60 m or about 200 ft) have a mutualistic relationship with photosynthetic unicellular algae. The relationship provides corals with the majority of the nutrition and the energy they require. The waters in which these corals live are nutritionally poor and, without this mutualism, it would not be possible for large corals to grow. Some corals living in deeper and colder water do not have a mutualistic relationship with algae; these corals attain energy and nutrients using stinging cells on their tentacles to capture prey.

It is estimated that more than 4,000 fish species inhabit coral reefs. These fishes can feed on coral, the cryptofauna (invertebrates found within the calcium carbonate substrate of the coral reefs), or the seaweed and algae that are associated with the coral. In addition, some fish species inhabit the boundaries of a coral reef; these species include predators, herbivores, or planktivores. Predators are animal species that hunt and are carnivores or “flesh eaters.” Herbivores eat plant material, and planktivores eat plankton.

Watch this National Oceanic and Atmospheric Administration (NOAA) video to see marine ecologist Dr. Peter Etnoyer discusses his research on coral organisms.

Try It

It takes a long time to build a coral reef. The animals that create coral reefs have evolved over millions of years, continuing to slowly deposit the calcium carbonate that forms their characteristic ocean homes. Bathed in warm tropical waters, the coral animals and their symbiotic algal partners evolved to survive at the upper limit of ocean water temperature.

Together, climate change and human activity pose dual threats to the long-term survival of the world’s coral reefs. As global warming due to fossil fuel emissions raises ocean temperatures, coral reefs are suffering. The excessive warmth causes the reefs to expel their symbiotic, food-producing algae, resulting in a phenomenon known as bleaching. When bleaching occurs, the reefs lose much of their characteristic color as the algae and the coral animals die if loss of the symbiotic zooxanthellae is prolonged.

Rising levels of atmospheric carbon dioxide further threaten the corals in other ways; as CO2 dissolves in ocean waters, it lowers the pH and increases ocean acidity. As acidity increases, it interferes with the calcification that normally occurs as coral animals build their calcium carbonate homes.

When a coral reef begins to die, species diversity plummets as animals lose food and shelter. Coral reefs are also economically important tourist destinations, so the decline of coral reefs poses a serious threat to coastal economies.

Human population growth has damaged corals in other ways, too. As human coastal populations increase, the runoff of sediment and agricultural chemicals has increased, too, causing some of the once-clear tropical waters to become cloudy. At the same time, overfishing of popular fish species has allowed the predator species that eat corals to go unchecked.

Although a rise in global temperatures of 1–2˚C (a conservative scientific projection) in the coming decades may not seem large, it is very significant to this biome. When change occurs rapidly, species can become extinct before evolution leads to new adaptations. Many scientists believe that global warming, with its rapid (in terms of evolutionary time) and inexorable increases in temperature, is tipping the balance beyond the point at which many of the world’s coral reefs can recover.


Important Questions for CBSE Class 12 Biology Organisms and Its Environment

1.Ecology is the branch of biology, which studies the interactions among organisms and their physical (abiotic) environment.

2.The subject ecology is basically concerned with four levels of biological organisation.
These are given below:
(i)Organism Living component of the environment at individual level and is basic unit of ecological hierarchy.
(ii)Population The sum total of all individuals of a species in a specific geographical area.
(iii)Communities Assemblage of all the populations of different species present in an area that interact among themselves.
(iv)Biome It is a large unit, which consists of a major vegetation type, associated fauna in a particular climatic zone. Tropical rainforest, deciduous forest, sea coast, deserts, etc., are the major biomes of India.
NOTE Other important terms used in ecology are:
Ecosystem Represents, the organisms and their environment in a particular area.
Habitat It refers to a specific place or locality delimited by a combination of factors, physical features and barriers where a community dwells.
Niche The ecological niche of an organism represents the physical space occupied by it, the resources it utilises and its functional role in the ecological system.
Biosphere The surface of earth with all life forms, i.e. union of all ecosystems. It is a highly ordered system.

3.Environment Ecology at organism level deals with how different organisms are adapted to their environment in terms of their survival and reproduction.
(i)Different biomes are formed due to: .

  • annual variations in the intensity and duration of temperature.
  • annual variations in precipitation.

The major biomes of the world are desert, grassland, rainforest and tundra.

(ii)Regional and local variations within each biome lead to the formation of a wide variety of habitats.
(iii) Life on earth exists in favourable habitats as well as in extreme and harsh habitats like scorching Rajasthan desert, rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, permafrost polar regions, high mountain tops, boiling thermal springs and stinking compost pits and even in our intestine.
(iv) The biotic components of a habitat are pathogens, parasites, predators and competitors of the organism with which they interact constantly.
(v)The key abiotic elements that lead to variations in habitats are:
(a)Temperature (b) Water
(c)Light (d) Soil.

4.Major abiotic factors are:
(i)Temperature is the major abiotic factor, which is most ecologically relevant.

  • There is seasonal variation in average temperature of land.
  • It decreases progressively from the equator to the poles and from plain areas to the mountains.
  • The range of temperature varies from sub-zero levels in polar areas to >50°C at high altitude in tropical deserts during summer.
  • The temperature affects the kinetics of body enzymes and thus, the basal metabolism and other physiological functions of the organism.
  • Based on tolerance of temperature range, organisms can be divided as:

Euiythennal These can tolerate a wide range of temperature.
Stenothermal These can tolerate a narrow range of temperature
(ii)Water is the next major important factor without which life cannot exist.

  • The productivity and distribution of plants in an environment depends on amount of water available.
  • For aquatic organisms, the quality (chemical composition and pH) of water is important.
  • Salinity refers to salt concentration (measured in parts per thousand) of water. Salt concentration is less than 5 in land water, 30-35 in sea and more than 100 in some hyper saline lagoons.
  • Based on tolerance of range of salinity, organisms can be grouped as:

Euryhaline Organisms, which can tolerate a narrow range of salinity.
Stenohaline Organisms, which can tolerate a narrow range of salinity.

  • Many freshwater animals cannot live for long in seawater and vice versa because of the osmotic problems they would face.

(iii)Light is an essential factor for the process of photosynthesis performed by autotrophs.

  • Oxygen is released during photosynthesis.
  • Many small plants like herbs and shrubs can perform photosynthesis under very low light conditions because they are overshadowed by tall, canopied trees.
  • Most of the plants also depend on sunlight to meet their photoperiodic requirement for flowering.
  • Light is also important for many animals as they use the diurnal and seasonal variations in light intensity and difration (photoperiod) as cues for timing their foraging, migratory and reproductive activities.
  • The UV component of solar radiation is harmful to many organisms. All the colour components of the visible spectrum are not available for marine plants living at different depths of the ocean.

(iv)Soil The nature and properties of soil vary from place to place. It depends on climate, weathering process and whether soil is transported or sedimentary and how its development occurred.

  • The soil composition, grain size and aggregation determine the percolation and water holding capacity of the soils.
  • The characteristics like pH, mineral composition and topography determine the vegetation of an area.
  • This in turn dictates the type of animals supported.

5.Responses to abiotic factors determines how organisms can cope or manage with stressful conditions of the habitat.
(i)During the course of millions of years of their existence, many species would have evolved a relatively constant internal (within the body) environment that permits all biochemical reactions and physiological functions to proceed with maximal efficiency and thus, enhance the overall fitness of the species.
(ii)The organisms should try to maintain the constancy of its internal environment,i.e.homeostasis, despite of varying external environmental conditions that tend to upset its homeostasis.
(iii)Human beings can maintain their homeostasis by using artificial means
(air conditioner in summer and heater in winter).
(iv)Ways by which other organisms can cope up with environmental changes are given below:
Regulate

  • Some organisms maintain homeostasis by physiological and sometimes behavioural means.
  • All birds and mammals and few lower vertebrates and invertebrates are capable of thermoregulation and osmoregulation.
  • In mammals, during summer, sweating occurs profusely and the evaporation brings down temperature of the body.
  • In mammals, during winter, shivering occurs which is a kind of exercise that produces heat and raises the body temperature.
  • Plants, on the other hand, do not have such mechanisms to maintain their internal temperature.
  • About 99% of animals and almost all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature.
  • In aquatic organisms, the osmotic concentration of the body fluids change with that of the osmotic concentration of the ambient water. These animals and plants are called
  • Thermoregulation is energetically expensive for many organisms. This is specially true for small animals like shrews and humming birds.Heat loss or gain is a function of surface area. Since, smal^animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside they have to expend much energy to generate body heat through metabolism. This is the reason that very small animals are rarely found in polar regions.
  • It can be concluded that during the course of evolution, some species have evolved the ability to regulate but only over a limited range of environmental conditions, beyond which they simply conform.

Migrate
It is the temporary movement from a stressful habitat to a more hospitable area and
return, when the stressful period is over.

  • Many animals, particularly birds, during winter undertake long-distance migrations to more hospitable areas.
  • Every winter the famous Keolado National Park in Bharatpur (Rajasthan) hosts, thousands of migratory birds coming from Siberia and other extremely cold Northern regions every winter.
  • Under unfavourable conditions bacteria, fungi and lower plants slow down their metabolic rate and forms a thick-walled spore to overcome stressful conditions. These spores germinate under onset of suitable environment.
  • In higher plants, seeds and some other reproductive structures serve as means to tide over periods of stress. They reduce their metabolic activity and undergo dormancy.
  • Some animals, which fail to migrate might avoid the stress by escaping in time. For example, Bear undergoes hibernation during winter.
  • Some snails and fish undergo aestivation to avoid summer related problems.
  • During unfavourable conditions, many zooplanktons in lakes and ponds enter diapause (a stage of suspended development)

6.Adaptation is any attribute of an organism, i.e. morphological, physiological or behavioural, that enables the organism to survive and reproduce in its habitat. Many adaptations have evolved over a long evolutionary time and are genetically fixed.
Some examples of adaptations are:
(i)Adaptations in kangaroo rat

  • The kangaroo rat in North American deserts is capable of meeting all its water requirements by internal oxidation of fat (water is a byproduct) in the absence of water.
  • It can concentrate its urine, so that minimal volume of water is used to expel excretory products.

(ii)Adaptations in desert plants

  • Many desert plants have a thick cuticle on their leaf surfaces and have their stomata arranged in deep pits to minimise water loss through transpiration.
  • They have special photosynthetic pathway (CAM) that enables their stomata to remain closed during day time.
  • Some desert plants like Opuntia, have no leaves. They are reduced to spines and photosynthesis occurs in flattened stems.

(iii)Adaptations in mammals

  • Mammals from colder climates generally have shorter ears and limbs to minimise heat loss. This is called Allen’s rule.
  • In polar seas, aquatic mammals like seals have a thick layer of fat (blubber) below their skin that acts as an insulator and reduces loss of body heat

(iv)Adaptations at high altitudes in humans
(a)At high altitude places like Rohtang Pass near Manali (> 3500 m) and Mansarovar, in China occupied Tibet, people suffer from altitude sickness.
(b)Its symptoms are nausea, fatigue and heart palpitations.
(c)This is because at low atmospheric pressure of high altitudes, body does not get enough oxygen.
(d)The relief occurs gradually due to acclimatisation.
(e)The body cope up with this low oxygen stress by

  • Increasing red blood cells production.
  • Decreasing the binding affinity of haemoglobin.
  • Increasing the breathing rate.

(v) Adaptations in desert lizards (Behavioural response)

  • They absorb heat from the sun when their body temperature drops below the comfort zone.
  • They move into shade when the ambient temperature starts increasing.
  • Some species burrow into the soil and escape from the above ground heat.

Previous Year Examination Questions

1 Mark Questions

1.Give an example of an organism that enters ‘diapause’ and why?[Delhi 2014]
Ans.Many zooplanktons in lakes and ponds enter diapause. They enter diapause to escape unfavourable environmental conditions and to delay the overall development.

2.Mention how do bears escape from stressful time in winter. [Delhi 2013c]
Ans.Bears escape from stressful time in winter by going into hibernation

3.Write the basis on which an organism occupies a space in its community/natural surroundings.[All India 2013]
Ans.An organism occupies individual or species level in its community. This level is occupied on the basis of ecological level of organisation or ecological hierarchy. Individual-> Population -> Biotic community -> Biome

4.Why are some organisms called as eurythermals and some other as stenohaline? [Foreign 2011]
Ans.Organisms, which can tolerate and thrive in a wide range of temperatures are called as eurythermal while organisms, which can tolerate and thrive in a narrow range of salinities are stenohaline

5.Why are green plants not found beyond a certain depth in the ocean? [HOTS Delhi 2011]
Ans.Beyond a certain depth, green plants are not found, because light is unavailable in that zone.

6.Mention any two activities of animals, which get cues from diurnal and seasonal variations in light intensity, [Delhi 2011 c]
Ans.The two activities of animals which get cues from diurnal and seasonal variations in light intensity are:
(i) Timing their foraging
(ii) Migratory activities
(iii) Reproduction (any two)

7.How do animals like fishs and snails avoid summer related unfavourable conditions? [Delhi 2010]
Ans.Fish migrate and snails go into aestivation or summer sleep to avoid summer-related problems.

8.How do prickles help cactus survive in desert? Give two methods.[All India 2010 C]
Ans.The two methods by which prickles help cactus survive in desert are:
(i) By reducing and altering outer surface to reduce evaporation of water.
(ii) By providing defense against grazing animals.

9.Which one of the two, stenothermals or eurythermals shows wide range of distribution on earth and why?[HOTS Delhi 2008]
Ans.Eurythermals show a wide range of distribution on earth, as they can tolerate and thrive in a wide range of temperatures

10.When and why do some animals like snails go into aestivation?[All India 2008]
Ans.During stressful conditions of the habitat and inability to migrate, animals like snails undergo aestivation and protect themselves

11.Why is the polar region not a suitable habitat for tiny humming birds? [HOTS All India 2008]
Ans.Humming birds have a larger surface area compared to body volume. They tend to lose body heat very fast, when it is cold outside. Due to this, they need to spend more energy to generate body heat. Hence, polar region being a cold habitat is not suitable for tiny hummingbirds

12.When and why do some animals go into hibernation? [Foreign 2008]
Ans.When unfavourable conditions are for a short time and if the animals could not migrate, they undergo hibernation to avoid stressful winter conditions.

13.List any two physiological responses that help you to gradually get acclimatised to high altitudes when you go from the plains. [Delhi 2008 C]
Ans.The physiological condition or responses in order to get accl imatised to high attitudes are:
(i) To compensate low oxygen, the production of red blood cells is increased.
(ii) High haemoglobin content and its decreased binding capacity.
(iii) Faster breathing rate (any two).

14.Define homeostasis. [All India 2008 C]
Ans.The process to maintain the constancy of internal environment of the body, despite varying external environmental conditions is called homeostasis

15.When and why do some animals like frogs hibernate? [Delhi 2008]
Ans.When unfavourable conditions are for a short time period and animals are unable to migrate, they hibernate to avoid the stres winter.

16.Between amphibians and birds, which will be stable to cope with global warming? Give reason.[HOTS All India 2008]
Ans.Birds will be stable to cope with global warming because they can tolerate a wide range of temperatures (eurythermals).

17.How do herbs and shrubs survive under the shadow of big canopied trees in forests? [Delhi 2008C]
Ans.The herbs and shrubs are adapted to perform photosynthesis optimally under very low light conditions due to growing in the forests under the shadow’ of big canopied trees

18.Why many of the freshwater animals cannot live for long in seawater or vice versa?[HOTS Delhi All India 2008 C]
Ans.Seawater contains high quantity of salt that is not favourable for freshwater animals. They face osmotic problems, hence they cannot survive in seawater for long.

2 Marks Questions

19.Some organisms suspend their metabolic activities to survive in unfavourable condition. Explain with the help of any four examples.[Delhi 2012]
Ans.Examples of organisms that suspend their metabolic activities in unfavourable condition.
(i) Bacteria, fungi and lower plants They form thick-walled spores, which help them to survive in unfavourable conditions. Spores germinate on return of favourable conditions.
(ii) Higher plants Seeds and some other vegetative reproductive structures serve as means to tide over periods of stress. They reduce their metabolic activity and undergo dormancy.
(iii) Animals They undergo hibernation or aestivation, if unable to migrate. For example, some snails and fishes.
(iv) Zooplanktons They enter diapause (suspended development) under unfavourable conditions.

20.Explain the response of all communities to environment over time. [All India 2011]
Ans.Response of communities to environment:
(i) Some organisms maintain homeostasis by physiological or behavioural means (regulate).
(ii)The internal environment in majority of animals and nearly all plants change with the change of external environment (conform).
(iii)Some organisms leave their habitats temporarily during unfavourable conditions and return back when conditions become favourable (migrate).
(iv)Some organisms suspend their metabolic activities to avoid stress by timely escaping, e.g. hibernation and aestivation.

21.Bear hibernates, whereas some species of zooplanktons enter diapause to avoid stressful external conditions. How are these two ways different from each other?[Foreign 2011]
Ans.Difference between diapause and hibernation:

22.How does our body adapt to low oxygen availability at high altitudes?[Foreign 2011]
Ans.Body adaptations at high altitudes are:
The physiological condition or responses in order to get accl imatised to high attitudes are:
(i) To compensate low oxygen, the production of red blood cells is increased.
(ii) High haemoglobin content and its decreased binding capacity.
(iii) Faster breathing rate (any two).

23.Why are small animals rarely found in the polar regions? Explain.[HOTS Foreign 2010]
Ans.Small animals have a large surface area relative to their volume. So, they tend to lose body heat very fast during cold conditions. They need to spend more energy to generate body heat. Due to this smaller animals are rarely found in polar regions.

24.How do seals adapt to their natural habitat? Explain. [Foreign 2010]
Ans.Seals adapt to the natural habitat (cold climate) by developing a thick layer of fat (blubber) below their skin that acts as an insulator and reduce excess loss of body heat.

25.Humming birds v live among the bushes in tropics, while penguins live on icebergs. They cannot survive if their habitats are reversed. Justify. [HOTS Delhi 2010 C]
Ans.Humming birds are natural habitats of tropics. They have large surface area relative to their volume. So, they tend to lose heat very fast, even when it is cold outside.Penguins live on icebergs (natural habitat). They have less surface area to volume ratio. The lesser the ratio, more effective will be the thermoregulation. Also, they hide in group to escape from cold conditions. Therefore, both of them will not survive if their habitats are reversed

26.How does human body maintain constant temperature both in summers and winters? Explain.[Delhi 2009 C]
Ans.Human body maintains constant body temperature (37°C) as follows:
In summers, the outside temperature is very high than our body temperature. Due to this, profuse sweating occurs. This causes evaporation and cooling effect on the body.
In winters, the outside temperature is much lower than our body temperature. This causes shivering, a kind of exercise that produces heat and raises the body temperature.

3 Marks Questions

27.(i)State how the constant internal environment is beneficial to organisms.
(ii)Explain any two alternatives by which orgnaisms can overcome stressful external conditions.[All India 2014]
Ans.(i)Constant internal environment is beneficial to organisms as it permits all biochemical reactions and physiological functions to proceed with maximal efficiency, thereby enhancing the overall efficiency of organism.
(ii) The two alternatives by which organisms can overcome stressful external conditions are

  • Migration-organisms move temporarily to a favourable area under stressful conditions and return back when the period is over.
  • Hibernation and aestivation are ways to escape the stress during winters and summers respectively.

28.Water is very essential for life. Write any three features both for plants and animals which enable them to survive in water scarce environment,
or
How do organisms cope with stressful external environmental conditions which are localised or of short duration? [ah India 2011]
Ans.Adaptation in plants
(i) Thick cuticle on their leaf surface.
(ii) Stomata are arranged in deep pits (sunken) to minimise water loss through transpiration.
(iii) Leaves are reduced to spines. The photosynthetic function is carried out by thick, fleshy flattened stems.
Adaptation in animals
(i) Kangaroo rat meets the water requirement through internal oxidation of fat. They concentrate their urine, so that minimum volume of water is excreted.
(ii) Snails undergo aestivation during summers.
Organisms either migrate or suspend their metabolic activities when conditions are stressful for short duration.In such conditions, organisms are as follow:
(i) Moving away from stressful habitat to more favourable area and return to their habitat when stressful period is over. For example, birds from Siberia and other cold countries migrate to Bharatpur Sanctuary of Rajasthan.
(ii) Hibernating (frogs) or aestivating (snails) or undergo diapause (zooplanktons).
(iii) Thick-walled spores are formed in stressful conditions and germinate under suitable conditions, e.g. bacteria, fungi and lower groups of plants.

29.How do organisms like fungi, zooplanktons and bears overcome the temporary short-lived climatic stressful conditions? Explain.[All India 2010 Delhi 2008]
Ans.(i)Fungi They produce various kinds of thick-walled spores to survive under unfavourable conditions, which germinate on return of favourable conditions.
(ii) Zooplanktons They enter diapause, a stage of suspended development under unfavourable conditions.
(iii)Bears They hibernate during winter to escape the time of unfavourable conditions.

30.The following graph represents the organismic response to certain environmental condition (e.g. temperature)

(i)Which one of these A or B depicts conformers?
(ii)What does the other line graph depict?
(iii)How do these organisms differ from each other with reference to homeostasis?
(iv)Mention the category to which human belong. [All India 2009]
Ans.(i)A depicts conformers.
(ii) The other line B depicts regulators.
(iii) Differences between conformer and regulator are:

(iv) Humans are regulators.

5 Marks Questions

31.(i) Explain giving reasons why the tourists visiting Rohtang Pass or Mansarovar are advised to resume normal active life only after a few days of reaching there.
(ii) It is impossible to find small animals in the polar regions. Give reasons. [All India 2012]
Ans.(i)Tourists visiting to Rohtang Pass near Manali (> 3500 m) may suffer from altitude sickness. They resume normal active life only after a week because in low atmospheric pressure at high altitudes, the body does not get enough oxygen. Gradually, the body compensates low oxygen availability by
(a)Increasing red blood cell production.
(b)Decreasing the binding affinity of haemoglobin.
(c)Increasing the breathing rate.
(ii)Small animals have a large surface area relative to their volume. So, they tend to lose body heat very fast during cold conditions. They need to spend more energy to generate body heat. Due to this smaller animals are rarely found in polar regions.

32.list the different ways by which organisms cope or manage with abiotic stresses in nature. Explain any three ways. [All India 2009c]
Ans.Organisms cope up with abiotic stress by:
(i)Regulating Some organisms maintain homeostasis by physiological and behavioural means. They are called regulators, e.g.

  • In summers, when outside temperature is more, we sweat profusely that results in evaporative cooling to bring down the body temperature.
  • In winters, when temperature is low, we shiver (a kind of exercise) that produces heat and raise the body temperature.

(ii) Conformating Organisms that cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. Such animals are called conformers. For example, small animals have larger surface area relative to their volume. They lose body heat very fast in low temperature. So, they expend energy to generate body heat through metabolism for adjusting.
(iii) Migrating The temporary movement of organisms from the stressful habitat to a more hospitable area and return when favourable conditions reappear is called migration. The long distance migration is very common in birds.

33.(i) List any four abiotic components that lead to variations in the physical and chemical conditions of habitats.
(ii) Explain the impact of these components on the distribution of organisms in different habitats.
[All India 2009 C]
Ans.(i)Temperature, water, light and soil.
(ii) (a) Temperature influences the kinetics of enzymes and thereby the metabolism and other physiological functions of the organisms.
Organisms may be eurythermal and can tolerate a wide range of temperature and stenothermal that can tolerate only a narrow range of temperature.
(b)Water is important to sustain life and productivity and distribution of plants is dependent on water.
Freshwater forms cannot thrive in sea water and vice versa.
(c)Light influences photosynthesis of plants. Light also influences the flowering in plants and timing of foraging, reproduction and migratory activities of animals.
Aquatic plants occupy different depths depending on their pigments and the light available.
(d)Soil influences vegetation by the water holding capacity, topography and its composition.
Important Questions for Class 12 BiologyClass 12 BiologyNCERT Solutions Home Page


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What is the Marine Biome? (with pictures)

The marine biome is basically the environment of the world’s oceans, and is a way of categorizing and understanding the life and general characteristics of undersea habitats. Biomes as a whole are ecological zones or regions that scientists use to classify plants, animals, and mineral nutrients. The marine biome is usually understood to cover oceanic life. Most of the time freshwater is its own category, and sometimes coral reefs are too, even though these occur in the ocean. There are usually five main zones in the biome, namely intertidal, pelagic, benthic, and abyssal, each with its own dominant plant and animal species. The diversity of life across these zones is usually quite abundant, and many researchers believe that the marine habitat is one of the richest in the world when it comes to the number of different life forms that coexist. Perhaps as a consequence, the biome is also particularly sensitive to pollution and human degradation. Problems related to temperature shifts and toxicity aren’t always immediately felt or noticed, but a growing number of scientists have been speculating that the oceans play a larger role in the stability of climates and environments on land than may have previously been believed. As such, protecting the ocean space and the life within it has become a priority for many people, industries, and governments.

Biome Basics

In its simplest sense, a biome is any specific habitat where the animals and plants share a common environment. There are a couple of different ways of categorizing these spaces the simplest system names only land-based and water-based systems, but the categorization can also be much more granular. Aquatic biomes are usually divided into marine, freshwater, and estuary, which is sort of a combination of the two — often where a river meets the sea, or where the ocean feeds into other predominantly freshwater systems. On land, common divisions include temperate forest, rainforest, savannah, grassland, desert, tundra, and alpine.

Marine Zones

Researchers often break the marine biome into five distinct zones, primarily corresponding to ocean depth. The boundaries are often somewhat fluid and are usually more estimations than fixed points, and there is some crossover when it comes to the life, climate, and habitat of each, particularly around the edges. The animals and plants that live in different parts and particularly different depths of the ocean can be pretty varied, though, which does make zoning distinctions useful in certain contexts.

The first zone when coming from the shore is usually the intertidal zone, which is where the ocean meets the land these waters are the shallowest and usually also the warmest, and are where most coral reefs are found. Many of these regions are profoundly impacted by the pull of the tides, and smaller creatures are often shifted from place to place very regularly. Next is the pelagic zone, which is often also known simply as the “open ocean.” This is deeper water where bigger fish and sea mammals like whales and dolphins live. Ocean currents bring a mix of colder and warmer waters, which helps sustain these and other creatures.

Things are darker and colder in the benthic zone, which is deeper ocean that doesn’t get much sunlight. Small shellfish, worms, sea stars, and various algae grow near the sea floor in this region, and some fish also make their home here. The darkest and deepest part of the biome is the abyssal zone, which is on or near the core tectonic plates of the earth the water here is usually very cold and completely cut off from light. Fungi, spores, and bacteria are usually the most plentiful life forms.

Circulation Patterns and Movement

The circulation patterns in the open ocean move in a horizontal manner and affect the upper surface waters. There is also vertical circulation and this has more of an influence on marine life. In the upwelling type of vertical circulation of ocean water, deep ocean water filled with dissolved nutrients travels into coastal surface waters and encourages plankton growth. Plankton, in turn, is the basis of the entire food chain throughout the oceans. In thermohaline circulation, the nutrient-rich waters rise and mix, but only in the polar regions where differences in the temperature, density, and salinity of the ocean water are distinct.

Relationship to Land Climate

Marine currents affect all the coastal areas and the winds usually match the water temperature. Since water does not heat up or cool down very quickly, there are only small changes in the biome but, over time, these can and often do lead to big shifts when it comes to the sustainability of certain species or groups of plants and animals. Everything in the ocean is usually connected, be it through a food chain or some symbiotic relationships. Changes in one place are often felt in many others. The changes may be small at first, but often build cumulatively over months and years.

Pollution and Other Dangers

The introduction of foreign materials to the ocean can and does impact the dynamics of the biome, often very negatively. The coast of Alaska, the Persian Gulf, and the Gulf of Mexico are some of the worst places for oil spills, for instance, which have caused major destruction of marine wildlife and plants. Dumping of trash and toxic wastes in the ocean by companies is another major issue affecting the world's water sources. Even the laziness of everyday citizens who dump their trash waterways or shipping companies who are irresponsible with waste removal are affecting life in the ocean and, through it, the overall health and life of the planet as a whole.


The coastal zone is the area where land and water meet and extends to ocean depths up to approximately 150 meters and it is also the area where most marine organisms live. The coastal marine waters are located over the continental shelf. These waters are shallow enough to allow sunlight to penetrate to the sea floor. This allows for photosynthesis to occur, which in turn provides food for fish and other living things.

The oceanic zone is the area of open ocean that extends beyond the continental shelf, where the ocean depth typically is greater than 100 to 200 meters. The depth of the sea floor in the oceanic zone can be deeper than 32,800 feet (10,000 meters), a depth greater than the height of Mount Everest. Most of the marine waters in the oceanic zone are too deep, dark, cold and devoid of nutrients to support living things.


Footnotes

Electronic supplementary material is available online at http://dx.doi.org/10.6084/m9.figshare.c.3827953.

Published by the Royal Society. All rights reserved.

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Riparian Zone Characteristics

Geography

The riparian zone is characterized by both its proximity to water and by the plants and animals present. In terms of location, the riparian zone is always directly adjacent to a moving body of water such as a stream, river, or estuary. Depending on the latitude of the river, the riparian zone may be reduced as the temperature gets colder. Since plants cannot grow at the highest latitudes, rivers here have little to no riparian zone. On the other end of the spectrum, tropical rainforests do not have distinguishable riparian zones because the forest encroaches directly on the banks of most rivers.

The riparian zone is most commonly observed in temperate regions with seasons, where the additional water from the stream or river allows large trees and shrubs to grow along the bank. The riparian zone is common along rivers in the plains and savannah biomes, which don’t get enough water from precipitation to grow large trees. Here, the riparian zone stands out and is easily identifiable from the surrounding biome.

Flora and Fauna

Large trees like oaks, cottonwoods, ash trees, and willows are prime members of the riparian zone community. These trees provide shelter and rich soil, under which smaller shrubs and vegetation can grow. While the trees limit the amount of light that reaches the stream, they also insulate the stream from experiencing the heating effects of direct sunlight. This increases the biodiversity within the stream, and allows many opportunistic feeders to come to the biome.

Animals like otters and musk rats love the abundance the riparian zone has to offer, as well as the protection it provides from larger predators like wolves and cougars. Other animals include frogs, lizards, and snakes, all attracted by the water and abundance of prey. Many aquatic bird species make their homes in riparian areas, including birds like ducks and dippers.


237 Aquatic Biomes

By the end of this section, you will be able to do the following:

  • Describe the effects of abiotic factors on the composition of plant and animal communities in aquatic biomes
  • Compare and contrast the characteristics of the ocean zones
  • Summarize the characteristics of standing water and flowing water freshwater biomes

Abiotic Factors Influencing Aquatic Biomes

Like terrestrial biomes, aquatic biomes are influenced by a series of abiotic factors. The aquatic medium—water— has different physical and chemical properties than air, however. Even if the water in a pond or other body of water is perfectly clear (there are no suspended particles), water, on its own, absorbs light. As one descends into a deep body of water, there will eventually be a depth which the sunlight cannot reach. While there are some abiotic and biotic factors in a terrestrial ecosystem that might obscure light (like fog, dust, or insect swarms), usually these are not permanent features of the environment. The importance of light in aquatic biomes is central to the communities of organisms found in both freshwater and marine ecosystems. In freshwater systems, stratification due to differences in density is perhaps the most critical abiotic factor and is related to the energy aspects of light. The thermal properties of water (rates of heating and cooling and the ability to store much larger amounts of energy than the air) are significant to the function of marine systems and have major impacts on global climate and weather patterns. Marine systems are also influenced by large-scale physical water movements, such as currents these are less important in most freshwater lakes.

The ocean is categorized by several areas or zones ((Figure)). All of the ocean’s open water is referred to as the pelagic realm (or zone). The benthic realm (or zone) extends along the ocean bottom from the shoreline to the deepest parts of the ocean floor. Within the pelagic realm is the photic zone , which is the portion of the ocean that light can penetrate (approximately 200 m or 650 ft). At depths greater than 200 m, light cannot penetrate thus, this is referred to as the aphotic zone . The majority of the ocean is aphotic and lacks sufficient light for photosynthesis. The deepest part of the ocean, the Challenger Deep (in the Mariana Trench, located in the western Pacific Ocean), is about 11,000 m (about 6.8 mi) deep. To give some perspective on the depth of this trench, the ocean is, on average, 4267 m or 14,000 ft deep. These realms and zones are relevant to freshwater lakes as well.


In which of the following regions would you expect to find photosynthetic organisms?

  1. the aphotic zone, the neritic zone, the oceanic zone, and the benthic realm
  2. the photic zone, the intertidal zone, the neritic zone, and the oceanic zone
  3. the photic zone, the abyssal zone, the neritic zone, and the oceanic zone
  4. the pelagic realm, the aphotic zone, the neritic zone, and the oceanic zone

Marine Biomes

The ocean is the largest marine biome. It is a continuous body of salt water that is relatively uniform in chemical composition in fact, it is a weak solution of mineral salts and decayed biological matter. Within the ocean, coral reefs are a second kind of marine biome. Estuaries, coastal areas where salt water and fresh water mix, form a third unique marine biome.

Ocean

The physical diversity of the ocean is a significant influence on plants, animals, and other organisms. The ocean is categorized into different zones based on how far light reaches into the water. Each zone has a distinct group of species adapted to the biotic and abiotic conditions particular to that zone.

The intertidal zone , which is the zone between high and low tide, is the oceanic region that is closest to land ((Figure)). Generally, most people think of this portion of the ocean as a sandy beach. In some cases, the intertidal zone is indeed a sandy beach, but it can also be rocky or muddy. The intertidal zone is an extremely variable environment because of action of tidal ebb and flow. Organisms are exposed to air and sunlight at low tide and are underwater most of the time, especially during high tide. Therefore, living things that thrive in the intertidal zone are adapted to being dry for long periods of time. The shore of the intertidal zone may also be repeatedly struck by waves, and the organisms found there are adapted to withstand damage from their pounding action ((Figure)). The exoskeletons of shoreline crustaceans (such as the shore crab, Carcinus maenas) are tough and protect them from desiccation (drying out) and wave damage. Another consequence of the pounding waves is that few algae and plants establish themselves in the constantly moving rocks, sand, or mud.


The neritic zone ((Figure)) extends from the intertidal zone to depths of about 200 m (or 650 ft) at the edge of the continental shelf (the underwater landmass that extends from a continent). Since light can penetrate this depth, photosynthesis can still occur in the neritic zone. The water here contains silt and is well-oxygenated, low in pressure, and stable in temperature. Phytoplankton and floating Sargassum (a type of free-floating marine seaweed) provide a habitat for some sea life found in the neritic zone. Zooplankton, protists, small fishes, and shrimp are found in the neritic zone and are the base of the food chain for most of the world’s fisheries.

Beyond the neritic zone is the open ocean area known as the pelagic or open oceanic zone ((Figure)). Within the oceanic zone there is thermal stratification where warm and cold waters mix because of ocean currents. Abundant plankton serve as the base of the food chain for larger animals such as whales and dolphins. Nutrients are scarce and this is a relatively less productive part of the marine biome. When photosynthetic organisms and the protists and animals that feed on them die, their bodies fall to the bottom of the ocean, where they remain. Unlike freshwater lakes, most of the open ocean lacks a process for bringing the organic nutrients back up to the surface. (Exceptions include major oceanic upwellings within the Humboldt Current along the western coast of South America.) The majority of organisms in the aphotic zone include sea cucumbers (phylum Echinodermata) and other organisms that survive on the nutrients contained in the dead bodies of organisms in the photic zone.

Beneath the pelagic zone is the benthic realm , the deep-water region beyond the continental shelf ((Figure)). The bottom of the benthic realm is composed of sand, silt, and dead organisms. Temperature decreases, remaining above freezing, as water depth increases. This is a nutrient-rich portion of the ocean because of the dead organisms that fall from the upper layers of the ocean. Because of this high level of nutrients, a diversity of fungi, sponges, sea anemones, marine worms, sea stars, fishes, and bacteria exist.

The deepest part of the ocean is the abyssal zone , which is at depths of 4000 m or greater. The abyssal zone ((Figure)) is very cold and has very high pressure, high oxygen content, and low nutrient content. There are a variety of invertebrates and fishes found in this zone, but the abyssal zone does not have plants because of the lack of light. Hydrothermal vents are found primarily in the abyssal zone chemosynthetic bacteria utilize the hydrogen sulfide and other minerals emitted from the vents. These chemosynthetic bacteria use the hydrogen sulfide as an energy source and serve as the base of the food chain found in the abyssal zone.

Coral Reefs

Coral reefs are ocean ridges formed by marine invertebrates, comprising mostly cnidarians and molluscs, living in warm shallow waters within the photic zone of the ocean. They are found within 30˚ north and south of the equator. The Great Barrier Reef is perhaps the best-known and largest reef system in the world—visible from the International Space Station! This massive and ancient reef is located several miles off the northeastern coast of Australia. Other coral reef systems are fringing islands, which are directly adjacent to land, or atolls, which are circular reef systems surrounding a former landmass that is now underwater. The coral organisms (members of phylum Cnidaria) are colonies of saltwater polyps that secrete a calcium carbonate skeleton. These calcium-rich skeletons slowly accumulate, forming the underwater reef ((Figure)). Corals found in shallower waters (at a depth of approximately 60 m or about 200 ft) have a mutualistic relationship with photosynthetic unicellular algae. The relationship provides corals with the majority of the nutrition and the energy they require. The waters in which these corals live are nutritionally poor and, without this mutualism, it would not be possible for large corals to grow. Some corals living in deeper and colder water do not have a mutualistic relationship with algae these corals attain energy and nutrients using stinging cells called cnidocytes on their tentacles to capture prey.

Watch this National Oceanic and Atmospheric Administration (NOAA) video to see marine ecologist Dr. Peter Etnoyer discuss his research on coral organisms.

It is estimated that more than 4,000 fish species inhabit coral reefs. These fishes can feed on coral, the cryptofauna (invertebrates found within the calcium carbonate substrate of the coral reefs), or the seaweed and algae that are associated with the coral. In addition, some fish species inhabit the boundaries of a coral reef these species include predators, herbivores, and planktivores , which consume planktonic organisms such as bacteria, archaea, algae, and protists floating in the pelagic zone.


Global Decline of Coral Reefs
It takes many thousands of years to build a coral reef. The animals that create coral reefs have evolved over millions of years, continuing to slowly deposit the calcium carbonate that forms their characteristic ocean homes. Bathed in warm tropical waters, the coral animals and their symbiotic algal partners evolved to survive at the upper limit of ocean water temperature.

Together, climate change and human activity pose dual threats to the long-term survival of the world’s coral reefs. As global warming due to fossil fuel emissions raises ocean temperatures, coral reefs are suffering. The excessive warmth causes the reefs to lose their symbiotic, food-producing algae, resulting in a phenomenon known as bleaching . When bleaching occurs, the reefs lose much of their characteristic color as the algae and the coral animals die if loss of the symbiotic zooxanthellae is prolonged.

Rising levels of atmospheric carbon dioxide further threaten the corals in other ways as CO2 dissolves in ocean waters, it lowers the pH and increases ocean acidity. As acidity increases, it interferes with the calcification that normally occurs when coral animals build their calcium carbonate shelters.

When a coral reef begins to die, species diversity plummets as animals lose food and shelter. Coral reefs are also economically important tourist destinations, so the decline of coral reefs poses a serious threat to coastal economies.

Human population growth has damaged corals in other ways, too. As human coastal populations increase, the runoff of sediment and agricultural chemicals has increased, as well, causing some of the once-clear tropical waters to become cloudy. At the same time, overfishing of popular fish species has allowed the predator species that eat corals to go unchecked.

Although a rise in global temperatures of 1–2 ˚C (a conservative scientific projection) in the coming decades may not seem large, it is very significant to this biome. When change occurs rapidly, species can become extinct before evolution can offer new adaptations. Many scientists believe that global warming, with its rapid (in terms of evolutionary time) and inexorable increases in temperature, is tipping the balance beyond the point at which many of the world’s coral reefs can recover.

Estuaries: Where the Ocean Meets Fresh Water

Estuaries are biomes that occur where a source of fresh water, such as a river, meets the ocean. Therefore, both fresh water and salt water are found in the same vicinity mixing results in a diluted (brackish) saltwater. Estuaries form protected areas where many of the young offspring of crustaceans, molluscs, and fish begin their lives, which also creates important breeding grounds for other animals. Salinity is a very important factor that influences the organisms and the adaptations of the organisms found in estuaries. The salinity of estuaries varies considerably and is based on the rate of flow of its freshwater sources, which may depend on the seasonal rainfall. Once or twice a day, high tides bring salt water into the estuary. Low tides occurring at the same frequency reverse the current of salt water.

The short-term and rapid variation in salinity due to the mixing of fresh water and salt water is a difficult physiological challenge for the plants and animals that inhabit estuaries. Many estuarine plant species are halophytes: plants that can tolerate salty conditions. Halophytic plants are adapted to deal with the salinity resulting from saltwater on their roots or from sea spray. In some halophytes, filters in the roots remove the salt from the water that the plant absorbs. Other plants are able to pump oxygen into their roots. Animals, such as mussels and clams (phylum Mollusca), have developed behavioral adaptations that expend a lot of energy to function in this rapidly changing environment. When these animals are exposed to low salinity, they stop feeding, close their shells, and switch from aerobic respiration (in which they use gills to remove oxygen from the water) to anaerobic respiration (a process that does not require oxygen and takes place in the cytoplasm of the animal’s cells). When high tide returns to the estuary, the salinity and oxygen content of the water increases, and these animals open their shells, begin feeding, and return to aerobic respiration.

Freshwater Biomes

Freshwater biomes include lakes and ponds (standing water) as well as rivers and streams (flowing water). They also include wetlands, which will be discussed later. Humans rely on freshwater biomes to provide ecosystem benefits, which are aquatic resources for drinking water, crop irrigation, sanitation, and industry. Lakes and ponds are connected with abiotic and biotic factors influencing their terrestrial biomes.

Lakes and Ponds

Lakes and ponds can range in area from a few square meters to thousands of square kilometers. Temperature is an important abiotic factor affecting living things found in lakes and ponds. In the summer, as we have seen, thermal stratification of lakes and ponds occurs when the upper layer of water is warmed by the sun and does not mix with deeper, cooler water. Light can penetrate within the photic zone of the lake or pond. Phytoplankton (algae and cyanobacteria) are found here and carry out photosynthesis, providing the base of the food web of lakes and ponds. Zooplankton , such as rotifers and larvae and adult crustaceans, consume these phytoplankton. At the bottom of lakes and ponds, bacteria in the aphotic zone break down dead organisms that sink to the bottom.

Nitrogen and phosphorus are important limiting nutrients in lakes and ponds. Because of this, they are the determining factors in the amount of phytoplankton growth that takes place in lakes and ponds. When there is a large input of nitrogen and phosphorus (from sewage and runoff from fertilized lawns and farms, for example), the growth of algae skyrockets, resulting in a large accumulation of algae called an algal bloom . Algal blooms ((Figure)) can become so extensive that they reduce light penetration in water. They may also release toxic byproducts into the water, contaminating any drinking water taken from that source. In addition, the lake or pond becomes aphotic, and photosynthetic plants cannot survive. When the algae die and decompose, severe oxygen depletion of the water occurs. Fishes and other organisms that require oxygen are then more likely to die, resulting in a dead zone. Lake Erie and the Gulf of Mexico represent freshwater and marine habitats where phosphorus control and storm water runoff pose significant environmental challenges.


Rivers and Streams

Rivers and streams are continuously moving bodies of water that carry large amounts of water from the source, or headwater, to a lake or ocean. The largest rivers include the Nile River in Africa, the Amazon River in South America, and the Mississippi River in North America.

Abiotic features of rivers and streams vary along the length of the river or stream. Streams begin at a point of origin referred to as source water . The source water is usually cold, low in nutrients, and clear. The channel (the width of the river or stream) is narrower than at any other place along the length of the river or stream. Because of this, the current is often faster here than at any other point of the river or stream.

The fast-moving water results in minimal silt accumulation at the bottom of the river or stream therefore, the water is usually clear and free of debris. Photosynthesis here is mostly attributed to algae that are growing on rocks the swift current inhibits the growth of phytoplankton. An additional input of energy can come from leaves and other organic material that fall downstream into the river or stream, as well as from trees and other plants that border the water. When the leaves decompose, the organic material and nutrients in the leaves are returned to the water. Plants and animals have adapted to this fast-moving water. For instance, leeches (phylum Annelida) have elongated bodies and suckers on the anterior and ventral areas of the body. These suckers attach to the substrate, keeping the leech anchored in place, and are also used to attach to their prey. Freshwater trout species (phylum Chordata) are an important predator in these fast-moving rivers and streams.

As the river or stream flows away from the source, the width of the channel gradually widens and the current slows. This slow-moving water, caused by the gradient decrease and the volume increase as tributaries unite, has more sedimentation. Phytoplankton can also be suspended in slow-moving water. Therefore, the water will not be as clear as it is near the source. The water is also warmer. Worms (phylum Annelida) and insects (phylum Arthropoda) can be found burrowing into the mud. The higher order predator vertebrates (phylum Chordata) include waterfowl, frogs, and fishes. These predators must find food in these slow moving, sometimes murky, waters and, unlike the trout in the waters at the source, these vertebrates may not be able to use vision as their primary sense to find food. Instead, they are more likely to use taste or chemical cues to find prey.

Wetlands

Wetlands are environments in which the soil is either permanently or periodically saturated with water. Wetlands are different from lakes because wetlands are shallow bodies of water whereas lakes vary in depth. Emergent vegetation consists of wetland plants that are rooted in the soil but have portions of leaves, stems, and flowers extending above the water’s surface. There are several types of wetlands including marshes, swamps, bogs, mudflats, and salt marshes ((Figure)). The three shared characteristics among these types—what makes them wetlands—are their hydrology, hydrophytic vegetation, and hydric soils.


Freshwater marshes and swamps are characterized by slow and steady water flow. Bogs, however, develop in depressions where water flow is low or nonexistent. Bogs usually occur in areas where there is a clay bottom with poor percolation of water. (Percolation is the movement of water through the pores in the soil or rocks.) The water found in a bog is stagnant and oxygen-depleted because the oxygen used during the decomposition of organic matter is not readily replaced. As the oxygen in the water is depleted, decomposition slows. This leads to a buildup of acids and a lower water pH. The lower pH creates challenges for plants because it limits the available nitrogen. As a result, some bog plants (such as sundews, pitcher plants, and Venus flytraps) capture insects in order to extract the nitrogen from their bodies. Bogs have low net primary productivity because the water found in bogs has low levels of nitrogen and oxygen.

Section Summary

Aquatic ecosystems include both saltwater and freshwater biomes. The abiotic factors important for the structuring of aquatic ecosystems can be different than those seen in terrestrial systems. Sunlight is a driving force behind the structure of forests and also is an important factor in bodies of water, especially those that are very deep, because of the role of photosynthesis in sustaining certain organisms.

Density and temperature shape the structure of aquatic systems. Oceans may be thought of as consisting of different zones based on water depth and distance from the shoreline and light penetrance. Different kinds of organisms are adapted to the conditions found in each zone. Coral reefs are unique marine ecosystems that are home to a wide variety of species. Estuaries are found where rivers meet the ocean their shallow waters provide nourishment and shelter for young crustaceans, mollusks, fishes, and many other species. Freshwater biomes include lakes, ponds, rivers, streams, and wetlands. Bogs are an interesting type of wetland characterized by standing water, lower pH, and a lack of nitrogen.

Visual Connection Questions

(Figure) In which of the following regions would you expect to find photosynthetic organisms?

  1. the aphotic zone, the neritic zone, the oceanic zone, and the benthic realm
  2. the photic zone, the intertidal zone, the neritic zone, and the oceanic zone
  3. the photic zone, the abyssal zone, the neritic zone, and the oceanic zone
  4. the pelagic realm, the aphotic zone, the neritic zone, and the oceanic zone

(Figure) B. Photosynthetic organisms would be found in the photic zone, the intertidal zone, the neritic zone, and the oceanic zone.

Review Questions

Where would you expect to find the most photosynthesis in an ocean biome?

A key feature of estuaries is:

  1. low light conditions and high productivity
  2. salt water and fresh water
  3. frequent algal blooms
  4. little or no vegetation

Critical Thinking Questions

Scientists have discovered the bodies of humans and other living things buried in bogs for hundreds of years, but not yet decomposed. Suggest a possible biological explanation for why such bodies are so well-preserved.

Bogs are low in oxygen and high in organic acids. The low oxygen content and the low pH both slow the rate of decomposition.

Describe the conditions and challenges facing organisms living in the intertidal zone.

Organisms living in the intertidal zone must tolerate periodic exposure to air and sunlight and must be able to be periodically dry. They also must be able to endure the pounding waves for this reason, some shoreline organisms have hard exoskeletons that provide protection while also reducing the likelihood of drying out.

Glossary


Curriculum

The sample course sequence below illustrates class offerings for the Biology major. Consult the official Xavier University course catalog for detailed registration and advising information.

  • BIOLOGY 160: General Biology I. 3cr.
  • BIOLOGY 161: General Biology I Lab. 1cr.
  • CHEMISTRY 160: General Chemistry I. 3cr.
  • CHEMISTRY 161: General Chemistry I Lab. 1cr.
  • CORE 100: 1st Year Seminar OR THEO 111. 3cr.
  • ENGLISH 101 OR 115 ENGL Compo or Rhetoric. 3cr.
  • CORE 101: GOA. 0cr.

Spring

  • BIOLOGY 162: General Biology II. 3cr.
  • BIOLOGY 163: General Biology II Lab. 1cr.
  • CHEMISTRY 162: General Chemistry II. 3cr.
  • CHEMISTRY 163: General Chemistry II Lab. 3cr.
  • CORE 100: 1st Year Seminar OR THEO 111. 3cr.
  • PHILOSOPHY 100: Ethics as Intro. 3cr.
  • CORE 102: GOA. 0cr.
  • CHEMISTRY 240: Organic Chemistry I. 3cr.
  • CHEMISTRY 241: Organic Chemistry I Lab. 1cr.
  • MATHEMATICS 140/170. 3cr.
  • PHILOSOPHY 200: Philosophical Perspectives Elective. 3cr.
  • Second Language I. 3cr.
  • Social Science Elective. 3cr.

Spring

  • BIOLOGY Elective. 3cr.
  • BIOLOGY 299: Professional Communication in the Sciences. 1cr.
  • CHEMISTRY 242: Organic Chemistry II. 3cr.
  • CHEMISTRY 243: Organic Chemistry II Lab. 1cr.
  • Historical Perspectives Elective. 3cr.
  • Second Language II. 3cr.
  • Theological Perspectives Elective. 3cr.
  • BIOLOGY Elective. 4cr.
  • BIOLOGY 410: Human Physiology. 3cr.
  • BIOLOGY 411: Human Physiology Lab. 2cr.
  • MATHEMATICS 146/156: Statistics. 3cr.
  • PHYS 160 College Physics I. 3cr.
  • PHYS 161 College Physics I Lab. 1cr.

Spring

  • BIOLOGY 230: Genetics. 3cr.
  • BIOLOGY 231: Genetics Lab. 1cr.
  • BIOLOGY Elective. 4cr.
  • Creative Perspectives Elective. 3cr.
  • General Elective. 3cr.
  • PHYSICS 162: College Physics II. 3cr.
  • PHYSICS 163: College Physics II Lab. 1cr.
  • BIOLOGY 496/497 or 498 Methods of BR I. 2cr.
  • BIOLOGY Electives. 5cr.
  • ENGLISH 205: Literature and Moral Imagination. 3cr.
  • Diversity Curriculum Requirement. 3cr.
  • General Elective. 3cr.

Spring

  • BIOLOGY 496/497 or 499 Methods of BR II. 2cr.
  • Biology Electives. 5cr.
  • E/RS Focus Elective. 3cr.
  • Humanities Elective. 3cr.
  • General Elective. 3cr.

Oceanography: things about the sea

Hi guys, a person I know has some theories on a particular spot in the ocean. The limited data he has found is inconclusive. I know this area has to have been surveyed for oil.

The coordinates are in the North Sea Roughly right here.

Any info would help. This is concerning old land formations that in theory were above water. Doggerland https://en.m.wikipedia.org/wiki/Doggerland

Which is currently a pretty hot topic in science.

15 9 6 11

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Drone shots always fascinates me

Important Summer Solstice Message

Are low tides getting lower?

I’ve been going to the same spot at the ocean in Hilo Hawaii for the past 25 years. A few months back I went on the morning after the new moon and the tide was so low that I kind of panicked, thinking a tsunami was on its way.

I managed to coincidentally go in the early morning again, the following month during the full moon low tide and noticed the tide even lower than the month before.

This morning I once again went to the beach after a full moon (this is never intentional) and this time the tide was even lower than the last two occasions. Ponds that are usually full of water were drained. The area I usually swim in was teaming with every species of fish (nice!) and the water was so still it was like an aquarium. All the coral were exposed. I even noticed sea cucumbers about 3’ above the water line.

There first time I noticed the low tide, I thought it was a special event. But now I’m wondering, as we have higher tides associated with sea level rise, are we also having lower low tides? I couldn’t find an answer anywhere, so I’m turning to the brilliant people of Reddit to tell me if there’s any correlation.


Watch the video: Aquatic Biomes. Biology (January 2022).