Population and Community

3.1 POPULATIONDonna.Roldan.Penton

biosphere

ecosystem

community

population

organism

What is population?

POPULATION

-- group of similar species/organism living in a certain place at the same time.

3.2 Characteristics of Population

Population Dynamics

Three Key Features of Populations

1. Size2. Density3. Distribution

SIZE-- pertains to the number of individuals in a population.

Example: The recorded population of people in the Philippines on July 2000 is 72, 000, 000.

KIND PLACE TIME NUMBER

Homo Sapiens

Philippines July 2000 72, 000, 000

FACTORS THAT AFFECTS THE SIZE OF A POPULATION

1. Natality -- numbers of species that are born

2. Mortality-- number of species that die

3. Immigration- numbers of species that entered

the land

4. Emigration- numbers of species that leave the land

Immigration

Emigration

Births DeathsPopulation

Change

++

-

-

Factors That Affect Population Growth

DENSITY

-- number of individuals or species living in a particular area of that population.

EXAMPLE:100 cows/hectare

DISTRIBUTION

-- describes the spacing of organisms relative to each other.

Patterns of Distribution:

1. Clumped Distribution2. Uniform Distribution3. Random Distribution

CLUMPED DISTRIBUTION

The organism are concentrated in an area. It may offer the population protection from enemies.

UNIFORM DISTRIBUTION

The organisms are evenly distributed over an area.

RANDOM DISTRIBUTION

There is no specific order in random distribution, the organism is spread throughout the area with-out an over-all pattern.

3.3 POPULATION GROWTH

SURVIVORSHIP and MORTALITY

The growth of a population depends upon the balance of mortality and natality.

BIOTIC POTENTIAL

It is the number of offspring that could exist if all offspring survived and produced young.

The life history of a housefly.

A female can lay 120 eggs and hatch them in one day. Within the sixth day, the pupa forms. In a week, adults emerge from the pupa. In the span of two weeks, single pair of flies produce 120 offsprings.

ENVIRONMENTAL RESISTANCE

Factors that reduces the growth rate of population. It is when a population does not reach its biotic potential because there are factors that affect its growth.

- resource shortage (water/food)- disease, competition of organisms, predation

Carrying Capacity- the maximum number of individuals in a particular population that the environment can support over an indefinite period of time in terms of food, space and shelter.

CARRYING CAPACITY

3.4 Limiting Factors of Population

1. Density-dependent factors

Biotic factors in the environment that have a greater limiting effect as population size increases.

 Examples:

disease competition parasites

2. Density-independent factors

Abiotic factors in the environment that affect populations regardless of their density.

 Examples:

temperature storms

habitat destruction drought

4.1 COMMUNITY

COMMUNITY

It is the place where populations interact.

Can considered from two viewpoints:

- Autecology – each organism is a member of a community

- Synecology – group of organisms in a particular area

4.2 SPECIAL RELATIONSHIP AMONG ORGANISMS

Biotic communities live and interact together. Interaction

between different trophic levels of organisms involves predation

and competition.

PREDATION

Predator:

consumer that captures and eats other consumers.

Prey: the organism that is eaten by a predator.

COMPETETITION

Competition doesn’t involve always the same species, but it is more severe among the same numbers of species because they have common needs.

4.3 SYMBIOTIC RELATIONSHIP

SYMBIOSIS

It means living together of two or more organisms of different species.

1. Parasitism: one organism benefits (the mosquito) while the other (the host) is harmed.

2. Mutualism: both species benefit.

3. Commensalism: one species benefits while the other remains unaffected.

4.4 COMMUNITY ROLES

Producers:

Organisms that make their own energy (food).

a. Use the process of photosynthesis.b. Oxygen is a by-product (waste material).

Consumers:

Organisms that can’t make their own food.Must eat producers or other consumers for energy.

Decomposers:

Organisms that feed on dead plants and animals.

4.5 ECOLOGICAL HABITATS AND NICHES

Habitat:

The place where an organism lives and that provides food, shelter, moisture, and temperature needed for survival.

Examples:a. Swampb. Field c. Laked. Tree

Where an organism lives.

Niche:

Role of an organism in the ecosystem, including unique ways an organism survives, such as: how it interacts with other organisms, how it obtains food and shelter, and avoids danger.

Examples:

a. Anteaters keep the ant population.b. Bacteria eats dead animals assisting in

decomposition. And keeping them from piling up, while adding nitrogen to the soil

Role an organism plays

4.5 ENERGY FLOWS/ENERGY TRANSFER/FOOD

CHAIN/FOOD WEB

TROPHIC PATTERN

Three Classifications of Consumers:

a. Herbivores: plant-eaters

b. Carnivores: animal-eaters

c. Omnivores: plant and animal eaters

Food Chains are basic representation of energy transfer from producers to consumers.

Food Webs demonstrate how the organisms are interconnected in a

more complex, realistic way.

Food Web