Ecology is the branch of biology that deals with the interactions among organisms and between organism and its physical (abiotic) environment.
Study of ecology is important to strike a balance between development and maintenance of natural environmental and biotic communities, use and conservation of resources, solve local, regional and global environmental problems.
It is basically concerned with four levels of biological organization – organisms, populations, communities and biomes.
Organism and its Environment
$\displaystyle \small \bullet$ Physiological ecology is the study of adaptation of an organism to environments in terms of survival and reproduction.
$\displaystyle \small \bullet$ The rotation of earth and the tilt of its axis cause annual variations in temperature and seasons.
$\displaystyle \small \bullet$ Major biomes (desert, rain forest, tundra etc.) are formed due to these variations and precipitation (rain and snow).
$\displaystyle \small \bullet$ Regional and local variations within a biome lead to the formation of different habitats.
$\displaystyle \small \bullet$ Life exists even in extreme and harsh habitats. E.g. Rajasthan desert, rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, Polar Regions, high mountain tops, thermal springs and compost pits.
$\displaystyle \small \bullet$ Our intestine is also a habitat for many microbes.
$\displaystyle \small \bullet$ The abiotic (physico-chemical) components (water, light, temperature, soil etc.) and biotic components (pathogens, parasites, predators, competitors etc.) lead to variation of different habitats.
Abiotic factors
Temperature
$\displaystyle \small \bullet$ It is the most important ecological factor to determine the bio-mass of a place. Average temperature on land varies seasonally and decreases progressively from the equator towards the poles and from plains to mountain tops.
$\displaystyle \small \bullet$ Temperature affects the kinetics of enzymes and basal metabolism along with physiological functions of the organisms.
$\displaystyle \small \bullet$ Based on range of thermal tolerance, organisms are 2 types
Eurythermal: They can tolerate a wide range of temperatures. Ex: cat, dogs , tigers etc.
Stenothermal: They can tolerate only a narrow range of temperatures. Ex: Penguin, fishes, crocodile.
Water
$\displaystyle \small \bullet$ It is the second most important factor. Life on earth is unsustainable without water. Productivity and distribution of plants is heavily dependent on water.
$\displaystyle \small \bullet$ For aquatic organisms the quality (chemical composition, pH) of water becomes important. The salt concentration (measured as salinity in parts per thousand), is less than 5 in inland waters, 30-35 in the sea and > 100 in some hypersaline lagoons.
$\displaystyle \small \bullet$ Based on the tolerance to salinity, organisms are 2 types
Euryhaline: Tolerate a wide range of salinities. Ex: Salmon, hierring etc.
Stenohaline: Tolerate only a narrow range of salinity. Ex. Goldfish and haddock
$\displaystyle \small \bullet$ Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems.
Light
$\displaystyle \small \bullet$ Sun is the ultimate source for light and temperature on land. Deep (>500m) in the oceans, the environment is dark and there is no energy available from sun.
$\displaystyle \small \bullet$ Plants need sunlight for photosynthesis.
$\displaystyle \small \bullet$ Small forest plants (herbs and shrubs) are adapted to photosynthesize optimally under very low light because they are overshadowed by tall, canopied trees.
$\displaystyle \small \bullet$ Many plants depend on sunlight for photoperiodism (e.g. flowering).
$\displaystyle \small \bullet$ Many animals use the diurnal and seasonal variations in light intensity and photoperiod for timing their foraging, reproductive and migratory activities.
$\displaystyle \small \bullet$ The spectral quality of solar radiation is also important for life.
$\displaystyle \small \bullet$ The UV spectrum is harmful to many organisms.
Soil
$\displaystyle \small \bullet$ The nature and types of soil changes in different places depending upon climate, weathering process, whether soil is transported or sedimentary and how soil development occurred.
$\displaystyle \small \bullet$ Soil composition, grain size and aggregation determine the percolation and water holding capacity of the soils along with pH, mineral, composition and topography determine the vegetation in any area.
$\displaystyle \small \bullet$ In the aquatic environment, the sediment characteristics often determine the type of benthic animals.
Responses to Abiotic Stress
$\displaystyle \small \bullet$ Organisms maintain a constant internal environment (homeostasis) despite varying external environmental conditions.
$\displaystyle \small \bullet$ There are various ways to establish homeostasis.
$\displaystyle \small \bullet$ The organisms cope up with changing environment in following ways
Regulate: It is the maintenance of homeostasis by physiological and behavioural means. It ensures constant body temperature (thermoregulation), constant osmotic concentration (osmoregulation) etc. E.g. All birds and mammals, very few lower vertebrates and invertebrates.
$\displaystyle \small \circ$ The success of mammals is mainly due to their ability to maintain a constant body temperature.
$\displaystyle \small \circ$ In human beings, in summer, when outside temperature is more than body temperature (37$\displaystyle ^{0}C$), sweating occurs. This results in evaporative cooling and brings down body temperature.
$\displaystyle \small \circ$ In winter, when the temperature is below 37$\displaystyle ^{0}C$, shivering occurs. It produces heat and raises the body temperature. Plants, on the other hand, do not have such mechanisms to maintain internal temperatures
Confirm: 99% of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature or osmotic concentration change with the surrounding conditions. They are called conformers.
$\displaystyle \small \circ$ In aquatic animals, osmotic concentration of body fluids changes with that of the ambient osmotic concentration.
$\displaystyle \small \circ$ Thermoregulation is energetically expensive especially for small animals (shrews, humming birds etc.). They have a larger surface area relative to their volume. So they lose body heat very fast when it is cold outside. Then they have to expend much energy to generate body heat. Therefore very small animals are rare in Polar Regions.
Migrate: The organisms move away for time being from the stressful unfavorable habitat to more suitable habitat and return back when stressful period is over. Many birds undertake long-distance to migrate to more hospitable areas. Siberia birds migrate to Keolado National park, Bharatpur, India.
Suspend: In microorganisms like bacteria, fungi and lower plants, a thick walled spores is formed which help them to survive unfavorable conditions. These spores germinate on return of suitable conditions.
$\displaystyle \small \circ$ In higher plants, seeds and some other vegetative reproductive structures serves the means to tide over periods of stress and help them in dispersal also. The metabolic activities are reduced to minimum during this dormant period.
Hibernation: the condition or period of an animal or plant spending the winter in a dormant state. E.g.: Bear
Aestivation: the condition or period of an animal or plant spending the summer to avoid heat and dessication in a dormant state. e.g snails.
Diapause: a stage of suspended development in zooplankton species in lakes and ponds.
Adapatations
$\displaystyle \small \bullet$ Adaptation is the morphological, physiological and behavioral attribute that enables an organism to survive and reproduce in its habitat.
$\displaystyle \small \bullet$ Many adaptations have evolved over a long evolutionary time and are genetically fixed.
$\displaystyle \small \bullet$ Kangaroo rat in North American deserts fulfill the water requirement by internal oxidation of fat in absence of water. It also has the ability to concentrate its urine so that minimal volume of water is used to remove excretory products.
$\displaystyle \small \bullet$ Thick cuticle in many plants also prevents loss of water. CAM plants open their stomata during night to reduce the loss of water during photosynthesis.
$\displaystyle \small \bullet$ Mammals from colder climates have shorter ears and limbs to minimize heat loss. This is called Allen’s Rule.
$\displaystyle \small \bullet$ In polar seas aquatic mammals like seals have a thick layer of fat called blubber, below their skin that acts as an insulator and reduces loss of body heat.
$\displaystyle \small \bullet$ At a high-altitude place (>3,500 m) we feel altitude sickness with symptoms like nausea, heart palpitations and fatigue. This is due to low atmospheric pressure. The body does not get enough $\displaystyle O_{2}$. Gradually, we acclimatize the situation and the body compensates low $\displaystyle O_{2}$ availability by increasing RBC and breathing rate and decreasing the binding capacity of haemoglobin.
A number of marine invertebrate and fish live in temperature always less than zero and some lives in great depth in ocean where pressure is very high by array of biochemical adaptations.
$\displaystyle \small \bullet$ Desert lizards bask in the sun and absorb heat when their body temperature is low, but move into shade when the ambient temperature starts increasing.
$\displaystyle \small \bullet$ Some species burrow into the soil to hide and escape from the above-ground heat.
Study of ecology is important to strike a balance between development and maintenance of natural environmental and biotic communities, use and conservation of resources, solve local, regional and global environmental problems.
It is basically concerned with four levels of biological organization – organisms, populations, communities and biomes.
Organism and its Environment
$\displaystyle \small \bullet$ Physiological ecology is the study of adaptation of an organism to environments in terms of survival and reproduction.
$\displaystyle \small \bullet$ The rotation of earth and the tilt of its axis cause annual variations in temperature and seasons.
$\displaystyle \small \bullet$ Major biomes (desert, rain forest, tundra etc.) are formed due to these variations and precipitation (rain and snow).
$\displaystyle \small \bullet$ Regional and local variations within a biome lead to the formation of different habitats.
$\displaystyle \small \bullet$ Life exists even in extreme and harsh habitats. E.g. Rajasthan desert, rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, Polar Regions, high mountain tops, thermal springs and compost pits.
$\displaystyle \small \bullet$ Our intestine is also a habitat for many microbes.
$\displaystyle \small \bullet$ The abiotic (physico-chemical) components (water, light, temperature, soil etc.) and biotic components (pathogens, parasites, predators, competitors etc.) lead to variation of different habitats.
Abiotic factors
Temperature
$\displaystyle \small \bullet$ It is the most important ecological factor to determine the bio-mass of a place. Average temperature on land varies seasonally and decreases progressively from the equator towards the poles and from plains to mountain tops.
$\displaystyle \small \bullet$ Temperature affects the kinetics of enzymes and basal metabolism along with physiological functions of the organisms.
$\displaystyle \small \bullet$ Based on range of thermal tolerance, organisms are 2 types
Eurythermal: They can tolerate a wide range of temperatures. Ex: cat, dogs , tigers etc.
Stenothermal: They can tolerate only a narrow range of temperatures. Ex: Penguin, fishes, crocodile.
Water
$\displaystyle \small \bullet$ It is the second most important factor. Life on earth is unsustainable without water. Productivity and distribution of plants is heavily dependent on water.
$\displaystyle \small \bullet$ For aquatic organisms the quality (chemical composition, pH) of water becomes important. The salt concentration (measured as salinity in parts per thousand), is less than 5 in inland waters, 30-35 in the sea and > 100 in some hypersaline lagoons.
$\displaystyle \small \bullet$ Based on the tolerance to salinity, organisms are 2 types
Euryhaline: Tolerate a wide range of salinities. Ex: Salmon, hierring etc.
Stenohaline: Tolerate only a narrow range of salinity. Ex. Goldfish and haddock
$\displaystyle \small \bullet$ Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems.
Light
$\displaystyle \small \bullet$ Sun is the ultimate source for light and temperature on land. Deep (>500m) in the oceans, the environment is dark and there is no energy available from sun.
$\displaystyle \small \bullet$ Plants need sunlight for photosynthesis.
$\displaystyle \small \bullet$ Small forest plants (herbs and shrubs) are adapted to photosynthesize optimally under very low light because they are overshadowed by tall, canopied trees.
$\displaystyle \small \bullet$ Many plants depend on sunlight for photoperiodism (e.g. flowering).
$\displaystyle \small \bullet$ Many animals use the diurnal and seasonal variations in light intensity and photoperiod for timing their foraging, reproductive and migratory activities.
$\displaystyle \small \bullet$ The spectral quality of solar radiation is also important for life.
$\displaystyle \small \bullet$ The UV spectrum is harmful to many organisms.
Soil
$\displaystyle \small \bullet$ The nature and types of soil changes in different places depending upon climate, weathering process, whether soil is transported or sedimentary and how soil development occurred.
$\displaystyle \small \bullet$ Soil composition, grain size and aggregation determine the percolation and water holding capacity of the soils along with pH, mineral, composition and topography determine the vegetation in any area.
$\displaystyle \small \bullet$ In the aquatic environment, the sediment characteristics often determine the type of benthic animals.
Responses to Abiotic Stress
$\displaystyle \small \bullet$ Organisms maintain a constant internal environment (homeostasis) despite varying external environmental conditions.
$\displaystyle \small \bullet$ There are various ways to establish homeostasis.
$\displaystyle \small \bullet$ The organisms cope up with changing environment in following ways
Regulate: It is the maintenance of homeostasis by physiological and behavioural means. It ensures constant body temperature (thermoregulation), constant osmotic concentration (osmoregulation) etc. E.g. All birds and mammals, very few lower vertebrates and invertebrates.
$\displaystyle \small \circ$ The success of mammals is mainly due to their ability to maintain a constant body temperature.
$\displaystyle \small \circ$ In human beings, in summer, when outside temperature is more than body temperature (37$\displaystyle ^{0}C$), sweating occurs. This results in evaporative cooling and brings down body temperature.
$\displaystyle \small \circ$ In winter, when the temperature is below 37$\displaystyle ^{0}C$, shivering occurs. It produces heat and raises the body temperature. Plants, on the other hand, do not have such mechanisms to maintain internal temperatures
Confirm: 99% of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature or osmotic concentration change with the surrounding conditions. They are called conformers.
$\displaystyle \small \circ$ In aquatic animals, osmotic concentration of body fluids changes with that of the ambient osmotic concentration.
$\displaystyle \small \circ$ Thermoregulation is energetically expensive especially for small animals (shrews, humming birds etc.). They have a larger surface area relative to their volume. So they lose body heat very fast when it is cold outside. Then they have to expend much energy to generate body heat. Therefore very small animals are rare in Polar Regions.
Migrate: The organisms move away for time being from the stressful unfavorable habitat to more suitable habitat and return back when stressful period is over. Many birds undertake long-distance to migrate to more hospitable areas. Siberia birds migrate to Keolado National park, Bharatpur, India.
Suspend: In microorganisms like bacteria, fungi and lower plants, a thick walled spores is formed which help them to survive unfavorable conditions. These spores germinate on return of suitable conditions.
$\displaystyle \small \circ$ In higher plants, seeds and some other vegetative reproductive structures serves the means to tide over periods of stress and help them in dispersal also. The metabolic activities are reduced to minimum during this dormant period.
Hibernation: the condition or period of an animal or plant spending the winter in a dormant state. E.g.: Bear
Aestivation: the condition or period of an animal or plant spending the summer to avoid heat and dessication in a dormant state. e.g snails.
Diapause: a stage of suspended development in zooplankton species in lakes and ponds.
Adapatations
$\displaystyle \small \bullet$ Adaptation is the morphological, physiological and behavioral attribute that enables an organism to survive and reproduce in its habitat.
$\displaystyle \small \bullet$ Many adaptations have evolved over a long evolutionary time and are genetically fixed.
$\displaystyle \small \bullet$ Kangaroo rat in North American deserts fulfill the water requirement by internal oxidation of fat in absence of water. It also has the ability to concentrate its urine so that minimal volume of water is used to remove excretory products.
$\displaystyle \small \bullet$ Thick cuticle in many plants also prevents loss of water. CAM plants open their stomata during night to reduce the loss of water during photosynthesis.
$\displaystyle \small \bullet$ Mammals from colder climates have shorter ears and limbs to minimize heat loss. This is called Allen’s Rule.
$\displaystyle \small \bullet$ In polar seas aquatic mammals like seals have a thick layer of fat called blubber, below their skin that acts as an insulator and reduces loss of body heat.
$\displaystyle \small \bullet$ At a high-altitude place (>3,500 m) we feel altitude sickness with symptoms like nausea, heart palpitations and fatigue. This is due to low atmospheric pressure. The body does not get enough $\displaystyle O_{2}$. Gradually, we acclimatize the situation and the body compensates low $\displaystyle O_{2}$ availability by increasing RBC and breathing rate and decreasing the binding capacity of haemoglobin.
A number of marine invertebrate and fish live in temperature always less than zero and some lives in great depth in ocean where pressure is very high by array of biochemical adaptations.
$\displaystyle \small \bullet$ Desert lizards bask in the sun and absorb heat when their body temperature is low, but move into shade when the ambient temperature starts increasing.
$\displaystyle \small \bullet$ Some species burrow into the soil to hide and escape from the above-ground heat.
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