4. Ecology and Population Biology 4.1 Ecology and The Energy Cycle - - PowerPoint PPT Presentation

• 4. Ecology and Population Biology

4.1 Ecology and The Energy Cycle 4.2 Ecological Cycles 4.3 Population Growth and Models

4.4 Population Growth and Limiting Factors 4.5 Community Structure and Biogeography

4.1 Ecology and the Energy Cycle

What is ecology? eco – “home”

• logy – “study of”

The study of how

• rganisms interact and

influence (or are influenced by) their environment.

Ecosystem – a group of populations within a given area, plus the environment they live in Population – total number

• f a given species of
• rganism within an

ecosystem Organism – an individual

• f a specific species

Community – the populations that interact with each other within an ecosystem Biosphere – the portion of the earth that includes all living things *also includes atmosphere (air), lithosphere (ground), and hydrosphere (water)

Habitat – the physical place where a species lives, which includes all biotic factors (living) and abiotic factors (non- living) Niche – the role a species plays within an ecosystem, it’s place in the food chain

Ecological Cycles-

• rganisms interact with

their environment in

• rder to obtain the

resources and energy necessary to live, creating cycles of energy and resources that allow the community to survive

All life requires energy to live, and energy can neither be made nor destroyed When we talk about the energy cycle, we’re talking about a transfer of energy from one form to another

Animals that feed only on

• ther animals are called

carnivores. Animals that consume

• ther animals, as well

photosynthetic

• rganisms are
• mnivores.

The levels in the food chain are called trophic levels.

Tertiary (apex) Consumer Secondary Consumer Primary Consumer Primary Producer

Primary Producers are also called autotrophs, as they produce their

• wn food.

4.2 Ecological Cycles

Ecological Cycles-

• rganisms interact with

their environment in

• rder to obtain the

resources an energy necessary to live, creating cycles of energy and resources that allow the community to survive

4.3 Population Growth and Models

While there are a number

• f factors that support

growth of a population, the growth of a population is held in check by limiting factors that exist within the environment. This balance of growth is at equilibrium under normal, unchanging, conditions.

Two major factors affect the rate of population growth: Birth rate, or natality Death rate, or mortality When the birth rate is equal to the death rate, the rate of population growth is constant.

There are two models for describing population growth: The exponential curve (J curve) The logistic curve (S curve)

The exponential curve model describes a population where there is no limit on the population growth. Realistically, this type of growth only exists during initial population growth.

The logistic curve model describes a population where the limits on the population growth are beginning to have an impact, and population growth is reaching an equilibrium state.

4.4 Population Growth and Limiting Factors

The limiting factors that keep population growth in check can be either biotic or abiotic. Biotic means biological factors, like over- population and food

• supply. Abiotic means

physical factors, like fire and water conditions

As a general rule, the survival and establishment

• f an organism in an area

is dependent upon 1) The availability of necessary elements for life in the minimum quantity 2) The controlled and constant supply of those elements

Because a number of factors contribute to maintaining homeostasis, population growth and density are usually controlled by multiple factors. Population density = # of

• rganisms / area

Abiotic limiting factors (density-independent factors): the density of the population has no effect on the limiting factor. An example of this would be a forest fire. The density of populations in the area prior to the fire have no impact.

The limiting factors that are biotic are also called density-dependent factors; the density of the population can have a large impact on the limiting factor. An example of this is fecundity, or number of eggs, in round worms.

Species will compete for limited resources and they may move in or out

• f an area to find new

niches, a process called dispersion. Species may disperse via emigration, immigration, and migration.

In some rare cases,

• ne species will be

wiped out by the

• ther, a process

called competitive exclusion.

Species sharing a range can have various relationships with each other. A predator is an

• rganism that eats

another for food, it’s prey.

Species that interact with each other have a relationship called symbiosis. Mutualism is a symbiotic relationship where both parties benefit from the interaction.

Amensalism is where one species is neither harmed nor helped, while the

• ther is inhibited.

Parasitism is where one species benefits, and the

• ther is harmed.

The survival of a population is dependent upon maintaining a minimal viable population size. When the population drops below this size, there is the potential for extinction, or elimination

• f that species.

4.5 Community Structure and Biogeography

The limiting factors that keep population growth in check can be either biotic or abiotic.

Community structure – the characteristics of a specific community A community can be closed or open. An open community has indefinite boundaries, while a closed community has defined boundaries, called ecotones.

Communities grow and change over time, and sometime one community can take

• ver another, a

process called succession.

Biomes are large areas of land with similar climate, flora, and fauna. The earths biomes are divided into terrestrial and aquatic biomes.

Oceans may be thought of as consisting of different zones based on water depth and distance from the shoreline and light

• penetrance. Coral reefs,

estuaries, and the freshwater biomes (include lakes, ponds, rivers, streams, and wetlands) are all unique aquatic biomes.