Interdependencies between species

State the 5 main levels of ecological organisation

Cell, Organism, Population, Community, Ecosystem

Define Population

A group of organisms of the same species, living together in a geographic area.

Define Species

A group of organisms that can interbreed to produce viable, fertile offsprings.

Define community

Different species living together in a particular place at a particular time, interacting with one another.

Define Ecosystem

Multiple communities interacting with each other and their environment

Define ecological niche

The role that species occupy in an ecosystem

State the types of interactions between species

• Symbiosis

• Mutualism

• Commensalism

• Amensalism

• Parasitism

• Predation

• Competition

Define Symbiosis

When two very different organisms live and functions together in a close association, to the benefit of at least one of them.

Define Mutualism

Where the relationship between the individuals means that they both benefit

What are some examples of Mutualism

• Dogs and humans

• Clownfish and anemones

• Some birds and bigger animals

• Bees and flowers

Define Commensalism

Where there is a relationship between two organisms where one gains a benefit while the other experience no benefit or harm

What are some examples of Commensalism?

• Whales and barnacles

• Livestock and cattle egrets

Define Parasitism

A relationship where one organism obtains nutrients at the expense of another organism

What are some examples of Parasitism?

• Leeches

• Ticks

• Fleas

• Tapeworms

What’s the difference between Parasitism and Predation?

One does not immediately cause the host’s death while the other does

Define Predation

A relationship where one organism hunts and kills another organism for food.

What are some examples of Predation?

• Spiders and insects

• Sharks and fish

• Snakes and smaller animals

• Lions and wildebeest 

Define Amensalism

A relationship where one organism is harmed, whereas the other is not affected at all

What are some examples of Amensalism?

• Cattle and grass

Define Competition

Where two organisms are rivalling for the same pool of resources

What are some examples of Competition?

• Weeds competing for water and nutrients in a garden

• Males fighting for dominance/a mate

Define Keystone species

Organisms that play a larger role in maintaining the structure of an ecosystem than other species

What are the two common role of a Keystone species

• Apex predators

• Ecosystem engineers

Define Apex Predators

Refers to Organisms being at the “top of the food chain” as they have no natural predators

What are apex predators responsible for?

For controlling the numbers of their prey, which then impacts the number of their prey and other organisms

Define Ecosystem engineers?

Organisms that alter the physical environment of their ecosystem

What are Ecosystem engineers responsible for?

They end up helping to help provide plants opportunities to grow better, or provide animals with shelter

What are some examples of Ecosystem engineers?

• The greater bilby forages for food by digging pits. These pits allow water into the soil which creates an environment with nutrients for plants to grow.

• Beavers construct dams and wetlands, which allows for many fish to have a place to live and thrive

Define Distribution?

All the places where a particular species can be found

What are Endemic species?

species that are only found in one defined geographic area

Define Density

The number of individuals per unit of area or volume

Define Abundance

A total number of individuals in a population

What are the 4 processes that affects population size?

• Natality (births or generations)

• Mortality (deaths)

• Immigration (organisms moving into a population)

• Emigration (movement out)

What is Exponential Population Growth?

When the change in population is caused by only births and deaths.

What is Exponential Population Growth usually seen in?

Only in species with short generation time who give rise to large numbers of offspring. Usually only occurs for relatively short periods of time

Define Limiting factors

The scarcity of resources needed by a population; food, water, shelter, nutrients, light

Define Density Independent

The affect a population’s size regardless of the size or density of the population. Can occur to major changes or disturbances to the environment

Define Density Dependent

The effects of factors on population size increase as the population density increases

What are examples of Density Dependent?

• Competition for resources

• Predation

• Crowding

• Parasitism

• Infectious disease

What is Carrying Capacity?

When a population reaches the maximum and becomes relatively stable, the species has reached its maximum population size sustainable by the ecosystem