ORGANISMS AND POPULATION

COMMUNITY�

POPULATION

Group of individuals of any one kind of organisms

All the population occupying a given area

BIOME

Large regional system characterised by major vegetation type

ECOSPHERE

All the living organisms of the earth.

ORGANISMS AND ENVIRONMENT

• Environment – Different conditions in which organism lives.
• Abiotic factors – Light, temperature, salinity, pressure, water etc.
• These factors determine growth, distribution, number, behaviour and reproduction of an organism.

GEOGRAPHICAL RANGE OF A SPECIES

Organisms in a habitat interact with each other can be a part of a tropic level to form food chain or food web

Water concervation in camel

Homeostasis in marine fish

Homeostasis in fresh water fish

Ecological niche - example

• Grasshopper and cricket live in the same habitat.

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Ecological niche - example

TEMPARATURE

• Temparature is the degree of hotness or coldness.
• It influences metabolism, behaviour, reproduction, development and even death of organisms.
• Enzymes of organisms are temperature sensitive.
• Determination of sex, sex ratio, maturation of gonads, gametogenesis and reproduction are influenced by temperature.
• Temparature affects size and colouration of organisms.
• Temparature influences distribution of organisms. The tropics have higher diversity and density of population when compared to temperate and polar region.

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BERGMAN’S RULE

• Birds and mammal attain greater body size in colder region than warmer region.

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aLLEN’S RULE

• Warm blooded animals, living in colder climates, tend to have shorter limbs, ears and other appendages when compared to the members of the same species in warmer climates.

JORDON’S RULE

When water temperature is low some animals develop more number of vertebrae. When the temperature is high number of vertebrae is less.

VAN’T HOFF’S RULE

• With the increase of every 10°C the rate of metabolic activity doubles or with the decrease of every 10°C the rate of metabolic activity is halved.
• The effect of temperature on the rate of reaction is expressed in terms of temperature coefficient or Q₁₀ value.
• Q₁₀ value is = rate of reaction at X°C

rate of reaction at X - 10°C

• In the living system Q₁₀ value is about 2.0

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�ADAPTATIONS TO TEMPARATURE�

• Eurytherms – Organisms which can survive a wide range of temperature. (Cat, dog, tiger, human)
• Cold-eurythermy – Adaptataion to cold temparatures
• Stenothermy – Organisms which can tolerate only a narrow range of temperature. (Fish, frog, lizard, snake)
• Formation of spores and cysts (Entamoeba)
• Antifreeze protein (Arctic fishes)
• Hibernation (winter sleep), Aestivation (summer sleep) and migration are other adaptations to temperature.

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LIGHT

• The quality (wavelength or colour), the intensity and duration of light are significant for organisms.
• Light influences growth, pigmentation, migration, metabolism and reproduction.
• Light is essential for vision.

In cave dwelling organisms

where there is no light eyes are absent.

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• In birds gonads become more active with increasing light.

Water - properties

• Essential for soil formation (Pedogenesis)
• Medium for several ecosystems
• Heavier than air and impart greater buoyancy to the aquatic medium. This enables organisms to float at variable levels.
• Water can withhold large amount of heat. Thus lakes and oceans tend to maintain a relatively constant temperature and the biosphere is relatively thermostable.
• The maximum density of liquid water occurs

at 4°C. Below that, it expands. This enables

ice to float on the top of waterbodies. Only in

the surface, water bodies will freeze,

while below the surface water will be in liquied

form, sustaining life.

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soil

• Four major functions of soil are

* medium for plant growth

* stores and purify water

* modify earth’s atmosphere

* habitat for many organisms

WIND

• The two main causes of wind are 1. Differential heating between the equator and the poles 2. Rotation of earth (Coriolis effect)
• Wind helps in a) transport of pollen grains and seeds b) flight of birds

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• Absolute humidity : Total mass of water vapour present in a given volume or mass of air. Temperature is not considered.
• Relative Humidity: The amount of water vapour present in air at the same tempera
• ture. It is expressed as percentage.

Humidity

altitude

• As altitude increases, temperature and density of oxygen decreases.
• Due to low temperature, higher altitude receives snow instead of rain.
• When people move from plains to higher altitudes their RBC count increases, to cope with lower atmospheric oxygen and higher oxygen demand.

biomes

• Biomes are large regions of earth that have common vegetation and climatic condition.
• They spread across the continents.
• Characters of a biomes

* Latitude and longitude

* Climate and physiochemical environment

* Predominant plant and animal life

* Boundaries between biomes cannot be sharply defined

AQUATIC BIOMES

• Fresh water biomes (lakes, ponds and rivers)
• Brackish water biomes ( Estuaries / wetlands)
• Marine (coral reefs, pelagic zones and abyssal zones

Tundra biome

• Treeless plain in the northern parts of Asia, Europe and North America
• Winters are long with little daylight and summers are short, with long daylight hours.
• Precipitation is less than 250mm per year. Zone of Permafrost.
• Flora: willows, birches, mosses, grasses and sedges
• Fauna: Reindeer, arctic hare, musk ox, lemmings are herbivores. Carnivores are arctic fox, arctic wolf, bobcat and snowy owl and polar bears.
• Many birds like ducks and geese are migratory.

taiga boiome

• Winters are long and cold
• Summer temperature 10°C to 21°C
• Precipitation 380 to 1000 mm annually
• Flora : Coniferous trees such as spruce, fir and pine
• Fauna: Herbivores such as moose, elk deer, reindeer, squirrel,snow shoe hare and predatory pine martens, timber wolf, frizzly bear, black bear, bobcat and wolvorines.

grassland biome

• Occurs in temperate and tropical regions.
• Show hot summer, cold winter high winds and irregular rainfall.
• Flora: Purple needle grass, wild oats, foxtail, rye grass and buffalo grass.
• Fauna:

Herbivores: Antelope, bison, wild horse, jack rabbit, ground squirrel and prairie dogs. Indian: Elephant, Gaur, Rhino, Antelope.

Carnivores: coyotes, foxes, hawks and snakes.

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alpine boiome

• Zone between timberline and snowzone.
• Snow zone

Sub-Snow zone

Meadow zone

Shrub zone

Timber zone

• In India alpine zone exist at the height of 3600m above mean sea level.

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• Fauna: Poor animal distribution. Invertebrate occurs in lakes, streams and ponds
• Flora: Alpine Pbacelia, bear grass, bristlecone pine, moss campion, polylepis forest, pygmy bitterroot and wild potato.

Tropical forest

• Occur near the equator between 23.5° north and 23.5° south.
• Only rainy and dry seasons. Winter season absent.
• The length of day light is 12 hours. Average annual temperature 20°C- 25°C. Annual rainfall more than 2000 mm.
• Tree canopy is multi-layered and continuous.
• Fauna: Birds, bats, small mammals and insects.
• Flora: Orchids, bromeliads, vines, ferns, mosses and palms.

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Types of Tropical forest

• Evergreen rainforest: No dry season
• Seasonal rainforest: Short dry period
• Semi evergreen forest: Longer dry season
• Moist deciduous forest (monsoon): The length of the dry season increases further as rainfall decreases.

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Temparate forest

• Occurs in eastern North America, north eastern Asia and western and central Europe.
• Well defined seasons with distinct winter.
• Annual temperature -30°C to 30°C. Rainfall, 750-1500mm.
• Soil is fertile enriched with decaying litter.
• Canopy is moderately dense and allows light to pass.
• Flora: Trees such as oak, hickory, beech, hemlock, maple,

basswood, cottonwood, elm, willow and herbs.

• Fauna: Squirrels, rabbits, skunks, birds, deer, mountain

lions, bobcat, timber, wolf, fox and black bear.

Types of Temparate forest

• Moist conifer and evergreen broad-leaved forest: wet winters and dry summers.
• Dry coniferous forest: Low precipitation.
• Mediterranean forests: Precipitation more during winter.
• Temparate coniferous forest: Mild winter and high annual precipitation. (More than 2000 mm)
• Temparate broad leaved rainforest: mild frost free winter, high annual precipitation (more than 1500mm)

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Desert biome

• Annual rainfall is less than 500mm. Short busts of rain between long rainless periods.
• Soil is course textured, shallow, rocky or gravely. No subsurface water. Sand dunes are common.
• Mean annual temperature 20-25°C. The extreme maximum temperature ranges from 43.5 -49°C.
• Flora of hot deserts: Opuntia, Euphorbia and royleana.
• Fauna: Camel can tap available water, capable of storing sufficient water. Animal are nocturnal in habit. Indian spiny lizard, blackbuck, white footed fox.

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Cold Desert

• Cold winter with snowfall and high overall rainfall throughout the winter.
• Occur in the Antarctic, Greenland and the Nearctic realm, parts of USA and western Asia and Ladakh of India.
• Mean annual temperature -2°C -4°C. The mean summer temperature ranges from 21- 26°C. Mean annual rainfall, 150-250mm.
• Soil is heavy, silty and salty.
• Fauna: Jack rabbit, Kangaroo rats, Kangaroo mice, pocket mice, grasshopper mice, antelope and ground squirrel

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population

• A group of organisms of the same species which can interbreed among themselves, and occupy a particular space and function as part of a biotic community.

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population density

• The size of the population in relation to unit of space and time
• Total number of that species within a natural habitat.
• The size of the population can be measured in
• Abundance : Absolute number in a population
• Numerical density: Number of individual per unit area.
• Biomass density: Biomass per unit area.
• Ecological density: Actual area of habitat available to the species.

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natality

• Population increases by natality.
• Production of new individuals in the population by birth, hatching, germination. Fertility and Fecundity determines natality.

Birth rate (b) = number of births per unit time

average population

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• Population decline factor. Loss of individuals in unit time.
• Specific mortality: The number of deaths in original population after a lapse of period.

Death rate (d) = number of deaths per unit time

average population

• Population density increases mortality, natural calamities, predation, and desertion by parents.

mortality

population dispersion

• Populations have tendency to disperse in all direction, until some barriers are reached.
• MIGRATION: Mass population movement

(Migration of siberian crane to Vedanthangal)

• EMIGRATION: Occurs during overcrowding, to

avoid over exploitation and to find new areas.

• IMMIGRATION: If the population increases beyond the carrying capacity, it can result in increased mortality or decreased reproductive capacity.

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Age distribution

• The proportion of the three major age groups is its age distribution attribute.
• Rapidly growing population will have larger proportion of young individuals.
• Stable population will have an even distribution of various age groups.
• Declining population tend to have a larger proportion of older individuals.

Growth curves

J SHAPED GROWTH FORM

• When a population increases rapidly in an exponential proportion and then stops abruptly, they exhibit J shaped growth form.
• Example : Many insects flourish in rainy season and disappear at the end of the season.

S- SHAPED GROWTH FORM

• Population increases slowly at first then more rapidly and gradually slow down due environmental resistance.

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Population regulation

• Population does not increase indefinitely.
• Once the carrying capacity is reached population numbers remains static or fluctuate.
• DENSITY INDEPENDENT (EXTRINSIC) FACTORS

Availability of space, shelter, weather, food

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• DENSITY DEPENDENT (INTRINSIC) FACTORS

Competition, predation emigration, immigration and diseases.

Population interaction