Biodiversity

Biology ATAR Year 11

Biology 1AB

Biology 3AB

Keywords

Genetic biodiversity

Species biodiversity

Ecosystem biodiversity

Biodiversity index

Energy flowEnergy transferEnergy transformationFood chainFood webFood pyramidBiomassProductivity

Definitions

EcosystemSystem formed by organisms interacting with one

another and their physical environment CommunityAll the living organisms in a habitat; the living part of an

ecosystem PopulationA group of organisms of the same species living in a

defined geographic area Species The basic category or group in the naming system of

Linnaeus. Organisms that are grouped into the species usually closely resemble each other and interbreed.

Definitions

Nichethe role of an organism in an ecosystem, often

defined by the environmental, biological and other conditions in which it lives.

Biotic factorsRelating to the biological parts of the

environment as opposed to the abiotic (physical) parts

Abiotic factorsRelating to the physical parts of the

environment, as opposed to the biological (biotic) parts

Ecosystems

Ecosystems can be named according to:

Climate◦Worldwide scale: biomes

Habitat◦Freshwater, marine or terrestrial

Dominant organisms◦Named after the largest or most dominant

species eg. Mangrove forest

Biodiversity It can mean the variety

of habitats, living communities and ecological processes in an ecosystem.

It can mean the diversity of genetic characteristics within a species.

It can mean the variety of species in a given area.

Importance of biodiversityEcosystems depend on the combined

contributions of the individual organisms within them. The loss of any species can prevent that ecosystem from operating the way it should.

An ecosystem with a high level of

biodiversity is more resistant to environmental change.

Measuring biodiversity A biodiversity index is a

way of measuring biodiversity.

Scientists use different biodiversity indices to measure diversity, depending on what is being studied.

For some conservation studies, more than one measure may need to be used.

Measuring biodiversity Species Richness◦ The total number of species in an area (add them up!)

Species Evenness◦ How evenly the species are represented in the area.◦ e.g. do most of the individuals belong to one species?

Measuring biodiversity

Species richness is a qualitative description…◦ “how many different species can I see?”

More species does not always mean more biodiversity because there may not be many individuals of each species (evenness)

Species evenness is a quantitative measurementIt is a measure of the abundance of

individuals in each species.

Abundance can be measured…

Percentage cover – the proportion of each quadrat occupied by the species.

Population density – the number of individuals per quadrat

Species frequency – the proportion of quadrats with the species in it.

Measuring biodiversityWhen both species richness and

species evenness increase, there is by definition an increase in BIODIVERSITY.

Transfer of energy and matterComplex systems can be describes in terms of

inputs, processes and outputs

IPO model:Inputs processes outputs (+ storage)

ExamplePhotosynthesisInput = water & carbon dioxideProcess = photosynthesis (driven by sunlight)Outputs = oxygen, water & glucose

Energy flow in ecosystems

Energy flows through a community. Energy from

the sun is captured by plants and converted into

chemical energy which is then transferred along a

food chain and used by each of the organisms for

growth.At each link in a food chain, only 10 per cent of the

energy is transferred from one level to the next.

The rest of the energy is lost as heat or temporarily

trapped in uneaten matter such as bone or fur.Because the amount of available energy

decreases as we move up a food chain, most food

chains can only support four or five links.

Food chains & food webs

Food chains and food webs are examples of qualitative models.

Energy is transferred from one trophic level to the next. (10%)

Energy is also transformed from one trophic level to the next. (90%)

Consumers – mix ‘n match

Primary consumer

Secondary consumer

Top consumer

Omnivores

Scavengers

Detritivores

Decomposers

Dung beetle & earthworm

Shark & eagle

Kangaroo & sheep

Fur seal & dingo

Fungi & bacteria

Goanna & vulture

Human & bear

Trophic efficiencyAnimals differ in how

efficiently they use the energy from food and how much of that energy can be passed on the next trophic level.

Ectotherms will use less energy than endotherms

Smaller animals will use less energy than larger animals

Example

Plants to insects to birds

Plants to kangaroos

The first food chain is longer because more energy is passed onto the next trophic level.

The second food chain is very short because most of the energy from food is used (transformed) into heat and chemical energy

Food chainsA food chain is a feeding relationship

showing the transfer of energy through a chain of organisms

Food webs

Food webs are integrated food chains

Food webs are complex networks

A food web represents the many possible feeding relationships in an ecosystem.

Factors affecting their complexity:An organism can

occupy different trophic levels in different, interconnecting food webs

An organism can occupy multiple trophic levels in the same food web

Migration eg. salmon

Food websA food web, and therefore ecosystem, is more

stable when many diverse predator-prey links connect high and intermediate trophic levels.

Food webs

Food websName the producers.Name an animal

which has more than one food source and name its food source.

What is the advantage to the animal of using different food sources?

What role do bacteria play in the food web?

What is the role of detritus feeders?

Food pyramidsFood pyramids show the relationships

of different trophic levels in a food chain.

Trophic means ‘feeding’, and each trophic level in a food pyramid is a temporary energy storage step in a food chain or food web.

Food pyramids are quantitative models.

Stepped Pyramid

Why are trophic levels usually shown in the shape of a pyramid?

A pyramid shape is used because the transfer of matter and energy from one trophic level to the next is not very efficient. Only 10 per cent of matter and energy from one trophic level makes it to the next so each trophic level will be smaller than the previous one.

BiomassThe biomass of an ecosystem is the total dry weight of biological material in the community. It is measured in dry weight per unit area.

Biomass

Productivity Productivity in an

ecosystem is the rate at which biomass accumulates or energy is stored.

The amount of biomass produced per year varies between communities.

This is because the rate of productivity of the autotrophs varies according to a range of growth conditions such as:water availabilitylight intensitynutrient availabilitytemperature

Communities with producers that grow and survive have the largest biomass levels.

Community Productivity (kg/m2)

Rainforest 2.0

Woodland 1.2

Grassland 0.6

Desert 0.1

Coral reef 2.2

Open ocean 0.1

Swamp and marsh 1.5