Topic 2 Ecosystems

Objectives To define concepts and terms associated

with ecosystems To give an overview of how an

ecosystem works and the roles of energy and carbon

To look at pyramids of number and of biomass

To look at population interactions

Ecology Ecology is “the scientific study of the

abundance and distribution of organisms and the interactions that determine distribution and abundance.”

Begon and Townsend 2006

What does this really mean – try to give concrete examples.

Ecosystems What do you understand by an

ecosystem?

Can you name ecosystems?

Definition An ecosystem describes a distinct

ecological unit that consists of both the living and non-living elements within it. An ecosystem can be permanent, such as tundra or desert, or it can be seasonal, such as a wetland formed from spring rains.

Abiotic/Biotic factors

Light Soil type Underlying geology Temperature Humidity Oxygen concentration Soil acidity Exposure

Predation Competition Symbiosis Disease Grazing

Abiotic factors Biotic factors

Ecosystems

What makes up our ecosystem Plants present Animals present Animals moving in and out Bacteria and fungi present Energy coming in Energy leaving Physical factors that define the habitat: heat,

rainfall, soil type, bedrock, pH, exposure to wind, waves, flooding, morphology, light and shade.

Influence of man’s activities

Food webs Show the interrelationship of organisms

within an ecosystem as predator, prey, consumer and competitor.

Trophic levels Producer Primary consumer (herbivores) Secondary consumers Tertiary consumers Top predators Detritivores or decomposers Omnivores – may occupy several trophic levels. What is the original source of energy? Give examples of each level of a food chain

Food chain What does this actually show in terms of

energy? What happens to energy at each stage?

Photosynthesis 1. Fixes energy 2. Fixes Carbon 3. Produces Oxygen 4. Carbon/energy moves up the food

chain Some energy is fixed within the

ecosystem autochthonous Some is fixed outside and imported

allochthonous Some is exported

Energy transfer How is energy passed on used? Where is energy lost?

Understanding this, explain why farmers often choose to keep farm animals inside.

Energy inputs and outputs in grassland

Inputs to the ecosystem Outputs from the ecosystem

Sunlight Migrating animals

Carbon (in a lake)

Allochthonous Autochthonous

Pyramids of number and biomass

Pyramid of number Pyramid of biomass

Pyramids of number & biomass

Oak tree 1 Herbivorous insects 500 000

Predatory insects 25 000

Small insect eating birds 100

Hawk 1

Oak tree 50 000 kg

Herbivorous insects 500 kg

Predatory insects 50 kg

Small birds 1 kg Hawk 100g

Data Numerical Data Biomass

Plot these data to produce two pyramids for the same ecosystem

What did you observe

Key terms

Species Bronzy inca

One of some 340 hummingbird species known in the Americas

Groups of similar organisms with similar features capable genetically and geographically of interbreeding.

There may be many similar but distinct species in a family

Term Definition

Population Population Mexico has

hawksbill turtles populations in Baja California and Yucatan

These are separate but may mix with other populations of the same species.

A group of individuals of the same species living in the same area.

A population may be completely or partially isolated from others, or there may be extensive mixing

Habitat Habitat This Mexican

scorpion is one of over a hundred species found in the country. Its habitat is caves – how can you tell?

This is the physical place in an environment where an animal lives. Its address

Niche Turkey vulture This is a carrion eating

species. It eats freshly dead, not putrefying meat

It cannot cut into larger animals so must wait for the king vulture to do so

It does not kill live animals like the black vulture

This is the role it occupies in the ecosystem. It is like its job.

Community The plant and

animal species present on the ‘estepa’ surrounding the school form a typical community

Interacting populations of species within an area

The organisms making up an ecosystem