Immigration: The number of individuals who have come into the habitat from

elsewhere in a certain period of time.

Population Growth Models

The population growth models include:

Exponential Growth: With the limited supply of food, the population follows
exponential growth.

Logistic Growth: When the resources are finite and become limited sooner or
later, population growth is said to be logistic.

Population Interactions

This refers to the interaction between different populations. There are

various modes of population interaction. These include:

Predation

This is a type of interaction in which an organism kills and feeds on another

organism. The one who kills is known as the predator and the one who is
killed is the prey.

Competition

This is the type of biological interaction between different animals or species

in which both are harmed.

Parasitism

Parasitism is a type of interaction between species in which the parasite lives

inside the body of another organism and cause harm to it.

Commensalism

In this type of interaction, one organism benefits while the other is neither
benefitted nor harmed.
Mutualism

In this type of interaction, both the species or organisms are benefitted from
each other.

What is adaptation?

What is hibernation?

List out the importance of light to plants.

Distinguish between hibernation and aestivation.

What are the biotic and abiotic factors of living organisms?

ECOLOGY:Branch of Science which deals with relationship between organisms

& their physical & biological environment.

LEVELS OF ORGANISATION:

• Organisms- every individual of a species

• Population- individuals of the same species at a given place

• Communities- assembly of population of all different species living in

an area and interacting.

• Biomes- large unit of flora and fauna in a specific climatic zone

ENVIRONMENT

Sum of all biotic and abiotic factors that surround and influence an organism
in it’s survival and reproduction.

Factors affecting environment:

• Rotation of earth

• Seasonal and annual variation in temperature and precipitation

• Habitats
MAJOR BIOMES

1. Artic & Alpine Tundra

2. Coniferous Forest

3. Temperate Forests

4. Grassland

5. Tropical Forest

6. Desert

MAJOR ABIOTIC FACTORS

• Temperature

• Water

• Light

• Soil

Temperature

• Ecologically most imp. Factor

• Decreases progressively from equator towards pole and from plane to

mountain tops

• Polar Region and high altitudes- sub zero level Tropical deserts >
50°C

• Organisms survive only in suitable range of temperature

• Based on tolerance to temperature

- Eurythermal

Organisms that tolerate wide range of temperature

- Stenothermal

Organisms that tolerate only narrow range of temperature

Water

• Life on earth originated in water

• Productivity and distribution of plants depends on water

Based on tolerance to salinity

- Euryhaline

Organisms that can tolerate wide range of salinity

- Stenohaline

Organisms that can only tolerate narrow range of salinity

• Freshwater animals cannot live in sea water and vice versa because
of osmotic problems.

Light

• sunlight source of energy- photosynthesis

• Small plants (canopied by tall plants) adapted to photosynthesize at

low light conditions.

• Flowering dependent on sunlight

• Foraging, Reproductive and migratory activities of animals depend

on seasonal variation in light intensity

• UV component – harmful to organisms

Soil

Nature of soil depends on

I. Climate
II. Weathering process
III. Sedimentary or transported
IV. Soil development
Characteristics of soil

a. soil composition

b. grain size

c. aggregation- determine percolation and water holding capacity of soil

RESPONSES TO ABIOTIC FACTORS

Homeostasis: The ability of an organism to maintain the constancy of its

internal environment despite varying external environmental conditions.

ADAPTATIONS IN ORGANISMS

1. Kangaroo rat: internal fat oxidation to produce water as by product-

concentrated urine

2.Desert plants: thick cuticle, stomata in deep pits to minimize transpiration

and special photosynthetic pathway (CAM). Ex. OPUNTIA – leaves reduced to
spines, photosynthetic stems

3. Cold climate mammals: short ears and limbs to minimize heat loss. This is
Allen’s Rule.

4. People living at high altitude: increased RBC production and increased

breathing rate

5. Desert lizards: bask in sun when cold and move to shade when hot.

POPULATION

Group of individuals living in a well defined area which share or compete for
similar resources and potentially interbreed

Example: Lotus plants in a pond

 Bacteria in a culture plate

Population ecology is therefore, an imp. Area of ecology because it links

ecology to population genetics and evolution

POPULATION ATTRIBUTES

1.Birth rate- Average no. of young ones born in a period of time with
reference to the members of the population.

2. Death rates- Average no. of deaths in a period of time with reference to

the members of the population.

3.Sex Ratio- No. of females and males per 1000 individuals

4. Age pyramid: Plot of age distribution (% individuals of a given age or age

group)

It reflects whether growth is

(i) Expanding
(ii) Stable
(iii) Declining

POPULATION DENSITY:

Number of individuals present per unit area at a given time.

POPULATION GROWTH

Factors affecting change in population density

Food availability

Predation pressure

Weather
Density changes by change in four basic processes

(a) Natality - Increase population

(b) Immigration - Increase population

© Mortality - Decrease population

(d) Emigration - Decrease population

1.Natality (B) : Number of births during given period in the population that
are added to the initial density

2.Mortality (D) : Number of deaths in the population during a given period.

3.Emigration € : Number of individuals of the population who left the habitat

and went elsewhere during the given period

4. Immigration (I) : Number of individuals of the same species that have

come into the habitat from elsewhere during the time under consideration.

If N is the population density at time ‘t’, then its density at time ‘t+1’

Nt+1 = Nt + [(B + I) – (D + E)]

Population density will increase if (B+I) > (D+E)

GROWTH MODELS

EXPONENTIAL

LOGISTIC

EXPONENTIAL GROWTH

• When resources are unlimited, each species realizes its innate

potential to grow in no. – population grows exponentially

• N – Population size

B – Birth rates( per capita births)

 D – Death rates (per capita deaths

dN/dt – increase/decrease in N during time t

Then, dN/dt = (b – d)*N

Let (b – d) = r, then

dN/dt = r*N

Where, r – intrinsic rate of natural increase

For human population in 1981, r = 0.0205

Integral form of exponential growth eq.

Nt = N0ert

Where Nt = Population density after t

N0 =Initial population density

R = Intrinsic rate of natural increase

E = base of natural logarithms

• Species growing exponentially under unlimited resources reaches

enormous population density in short time.

LOGISTIC GROWTH

• No population has unlimited resources-leads to competition for

resources

• Fittest individual survive and reproduce

• Carrying capacity (K)- Maximum population density a habitat’s

resources can support

• When a population has limited resources it shows

Lag phase

Phase of acceleration

Asympote- population density = K

COMPETITION

Interaction either among individuals of same species or between individuals

of different species.

Occurs among closely related species but not always true

1. Unrelated species also compete- flamingo & fish compete for zooplankton

2. Feeding efficiency of a species reduce due to other species even if

resources are plenty – Abingdon tortoise.

Evidence for competition

Competitive release – species distribution restricted to small areas due to

competitively superior species.

GAUSE’S COMPETITION EXCLUSION PRINCIPLE

“Two closely related species competing for same resources cannot coexist
as the competitively inferior one will be eliminated.”

Resource partition- Two competing species avoid competition by diff.

feeding and foraging patterns-Mc Arthur (warblers foraging activities)

PARASITISM

It is the interaction where one species (parasite) depends on the other

species (host) for food and shelter, host is harmed.
Parasites and host self-evolve.

Adaptations of parasites

- Loss of unnecessary sense organs

- Hooks and sucker

- Loss of digestive system

- High Reproductive capacity

Parasites-

(i) Reduce the survival of host

(ii) Growth and reproductive rate are reduced
(iii) Render the host vulnerable to its predators by making them weak

Types of parasite

ECTOPARASITES-depend on external surface of host

Example – head lice on humans, ticks on dogs

ENDOPARASITES-take shelter within the body of the host organism

Example – Liverfluke, Plasmodium

MUTUALISM

It is interaction in which both the interacting species are benefited

Examples

1. Lichen – fungi and algae

2. Mycorrhizae – fungi and roots of higher plants

3. Pollination of plants by insects

4. Mediterranean orchid- sexual deceit for pollination- appears as female

bee
AMENSALISM

Interaction between two different species, in which one species is harmed

and the other species is neither harmed nor benefited. Example. Bacterial
culture, after few days fungus growth will be there on it like Pencillium, and
its secretions of chemical will kill bacteria, but no benefits to fungi.