Biodiversity Biology ATAR Year 11 Biology 1AB Biology 3AB
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 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