Ecology

Habitat -The place where an organism lives.

Population - All the organisms of the same species living in one habitat.

Community - The population of different species living in a habitat.

Abiotic Factors - Non-living factors of the environment, e.g. temperature.

Biotic Factors - Living factors of the environment, e.g. food.

Ecosystem - The interaction of a community of biotic and abiotic parts of the environment.

Organisms need things from the environment and other organisms to survive and reproduce:

• Plants need light and its territory, as well as water and mineral ions from the soil.
• Animals need their territory, food, water, and mates.

Organisms compete with other species (or the same species) for the same resources.

In a community, each species depends on other species for food, shelter, pollination and seed dispersal - this is called interdependence.

A major change in the ecosystem (one species becomes extinct) can have far-reaching effects.

A stable community is one in which the size of the populations of all species remains relatively constant over time.

The environment in which organisms live changes all the time.

The things that change are either abiotic (non-living) or biotic (living) factors.

These can have an effect on a community...

Abiotic factors are non-living factors. For example:

- Moisture level

- Light intensity

- Temperature

- CO2 level (for plants)

- Wind intensity and direction

- O2 level (for aquatic animals)

- Soil pH and mineral content 

A change in the environment could be an increase or decrease in an abiotic factor (an increase in temperature). These can affect the size of populations in a community.

This means they can also affect the population sizes of other organisms that depend on them.

FOR EXAMPLE:

• A decrease in light intensity, temperature or level of CO2 could decrease the rate of photosynthesis in a plant species.
  • This could affect plant growth and cause a decrease in population size.

Biotic factors are living factors. For example:

- New predators arriving

- Competition (One species may outcompete another species)

- New pathogens

- Availability of food 

A change in the environment could be an introduction of a new biotic factor, e.g. a new predator or pathogen.

These can affect the sizes of populations in a community which can have indirect effects because of interdependence.

For example:

• A new predator could cause a decrease in the prey population.
  • Red and grey squirrels live in the same habitat and eat the same food.
  • Grey squirrels outcompete the red squirrels - the population of red squirrels is decreasing.