Ecology

Unit 3

What is Ecology?

The study of interactions between organisms and their environment

Limiting Factor: Factors which cause a populations’ growth to slow or stop.

Biotic Factors: These factors include all the living things that live in an environment.

Abiotic Factors: These are all of the non-living things which can influence population growth.

Each organism plays a particular roll in the ecosystem

The balance of these factors determines which living things can survive in a particular environment

Population Density: The number of individuals/organisms in a certain geographic area.

More dense

Less dense

vs.

Density Limiting Factors

Density Dependent Factors:

• Factors which have an increasing effect as the population increases.

• So as the number of organisms goes up, the effect of these factors have also goes up.

Disease, competition, predators, parasites, food availability

Examples:

Density Limiting Factors

Density Independent Factors:

• Factors which affect populations regardless of their size or density

Drought, wildfire, severe weather, pesticides

Examples:

Life-History Patterns – Refers to an organism’s reproductive pattern, growth pattern, and life span.

Rapid life-history pattern: These organisms tend to have small body sizes, mature rapidly, reproduce early, and have short life spans. (Example: mosquitos)

Slow life-history pattern: These organisms tend to be larger species that live in stable environments. They reproduce and mature slowly, as well as being long lived. They maintain population sizes at or near the carrying capacity. (Example: elephants)

Population Ecology is the study of how and why populations change.

A population ecologist determines what factors influence the size, density, distribution and growth of a population.

Growth rate is the change in a populations’ size over time.

4 factors that effect the growth rate of a population:

1. Birth rate
2. Death rate
3. Immigration (In)
4. Emigration (Exit Out)

Types of Population Growth

Exponential Growth: The type of growth which occurs when a population size increases dramatically over a period of time. It appears as a J-shaped curve.

This could happen when a population is introduced to an uninhabited area.

Types of Population Growth

Logistic Growth: The type of growth where a population begins with a period of slow growth, followed by a brief period of exponential growth before leveling off at a stable size. This type of growth appears as an S-shaped curve.

This happens when resources are limited.

Carrying Capacity: The maximum number of individuals that an environment can support.

Population Crash: A dramatic decline in the size of a population over a short period of time.

Population Crash

Ecological Succession: A series of predictable change (biotic changes) that occur in a community over time.

There are 2 different types of ecological succession:

1. Primary Succession

2. Secondary Succession

Primary Succession: Establishment and development of an ecosystem in an area that is newly exposed and previously uninhabited.

Examples:

A newly cooled lava flow

Bare rock exposed after a retreating glacier

Rock exposed after a large meteorite impact

Landslides

Strip mines

Pioneer Species: The first organisms to live in a previously uninhabited area.

Lichens are two different species, fungus and algae that form a symbiotic relationship.

Examples: Lichens, mosses, grass, worms, and possibly small mammals or reptiles.

Pioneer species often help break down rock and/or produce organic material to help form a layer of soil.

Secondary Succession: The reestablishment of a damaged ecosystem in an area where the soil was left intact.

Examples:

Forest fires

Abandoned farmland

Floods