Population Dynamics

Every organism has a habitat and a niche.

A habitat differs from a niche. A habitat is all aspects of the area in which an organism lives. – biotic factors – abiotic factors An ecological niche includes all of the factors that a species needs to survive, stay healthy, and reproduce. –food –abiotic conditions –behavior

Think – Pair – Share In your own words, tell your partner the difference between habitat and niche Be prepared to share Habitat is WHERE an organism lives and the niche includes HOW it lives.

Interactions of Organisms

Organisms interact as individuals and as populations. Three Types of Interactions: 1.Competition 2.Predation 3.Symbiosis

Community Interactions Competition – When organisms try to use the same ecological resource (anything necessary for life) in the same place at the same time. – Competition is always bad for both organisms. – In direct competition there is a winner and a loser. Many times causes extinction of one species from the area.

Competition Two Types of Competition – Intraspecific competition – Interspecific competition Where have we seen these prefixes before?

Competition Two Types of Competition – Intraspecific competition: Competition within the same species. – Interspecific competition: Competition between two species.

Predation occurs when one organism captures and eats another.

Think – Pair – Share Do predators or prey directly control the population size? Be able to defend your answer.

Mutualism: both organisms benefit There are three major types of symbiotic relationships.

Mutualism

There are three major types of symbiotic relationships. Commensalism: one organism benefits, the other is unharmed.

Commensalism

There are three major types of symbiotic relationships. Parasitism: one organism benefits, the other is harmed

– Parasites meet their needs as ectoparasites (such as leeches) and endoparasites (such as hookworms)

Parasitism

Population Dispersion and Growth

Each population has a density, a dispersion, and a reproductive strategy.

Population dispersion refers to how a population is spread in an area. Geographic dispersion of a population shows how individuals in a population are spaced. Clumped dispersion Uniform dispersion Random dispersion

clumped There are three types of dispersion.

uniform There are three types of dispersion.

random There are three types of dispersion.

Populations grow in predictable patterns.

The size of a population is always changing. Four factors affect the size of a population. – immigration – births – emigration – deaths

Think – Pair – Share Which two factors make a population grow? Which two will make a population smaller?

Population growth is based on available resources. Exponential growth is a rapid population increase due to an abundance of resources.

Logistic growth is due to a population facing limited resources.

A population crash is a dramatic decline in the size of a population over a short period of time. Carrying capacity is the maximum number of individuals in a population that the environment can support.

Ecological factors limit population growth. A limiting factor is something that keeps the size of a population down.

Think – Pair – Share Give an example of something that keeps populations under control?

-Predation -Competition -Parasitism -Disease Density-dependent limiting factors are affected by the number of individuals in a given area.

Density-independent limiting factors limit a population’s growth regardless of the density. –unusual weather –natural disasters –human activities