life science ecosystem. grade 10
DESCRIPTION
TRANSCRIPT
Life scienceGrade 10
Ecosystem
Learning outcomes
At the end of this chapter learners should be able to:
Define ecosystem and other important terms
Draw and label a food web
Discuss the food pyramids and energy pyramids in details
Discuss biomass in details
Explain the energy transfer in the ecosystem.
ECOSYSTEMS
An ECOSYSTEM is all the different organisms in the world living together in a PARTICULAR ENVIRONMENTor HABITAT
Our own bodies are homes to tiny living organisms!
All the ecosystems combined together make up the BIOSPHERE
An ecosystem is an environment in which plants (flora) and animals (fauna) live.
Ecosystems survive through the interactions between plants and animals and an example of this is what are referred to as food chains and food webs.
Without these interactions, ecosystems risk breaking down and could be destroyed - we will look at this in more detail when we look at ecosystems under threat.
Ecosystem
The collection of organisms in an area along with the important environmental factors
Eg ocean ecosystem
An example ecosystem
Population
A population is the number of organisms of the same species living in a habitat
Community
All the animals and plants living in an ecosystem
Habitat
The area where animals and plants live
Eg ocean habitat
Or.. More specific Coral habitat
Trophic levels
The level occupied by a consumer in a foodchain is referred to as a feeding or TROPHIClevel.
Primary consumers occupy the 1st trophiclevel; secondary consumers occupy the 2nd trophic level, and so on.
Food Chain
A food chain is a linear sequence of links in a food web starting from a species that are
called producers in the web and ends at a species that is called decomposers species in
the web. A food chain also shows how the organisms are related with each other by the
food they eat. A food chain differs from a food web, because the complex polyphagous
network of feeding relations are aggregated into trophic species and the chain only
follows linear monophagous pathways. A common metric used to quantify food web
trophic structure is food chain length. In its simplest form, the length of a chain is the
number of links between a trophic consumer and the base of the web and the mean chain
length of an entire web is the arithmetic average of the lengths of all chains in a food web
Producer
Primary ConsumerHerbivore
Secondary ConsumerCarnivore
Tertiary ConsumerCarnivore
What happens if a link in the food chain is broken?
X
X
Food webs
The interrelationship between many food chains is called a food web.
BiomassBiomass is an estimate of the amount of matter in
a
given population of organisms. Biomass for different
trophic levels is compared in a biomass pyramid.
A biomass pyramid shows how the quantity of matter
in living things changes along a food chain.
Pyramid of Biomass
The base of the pyramid
represents the matter in
producers. The next level shows biomass of primary consumers and so on….
Biomass decreases as you go up the pyramid
An energy pyramid shows the total energy in
trophic levels and how that energy is lost
along a food chain.
Energy pyramid
DecomposersOrganisms that use the organic matter
of dead
plants and animals are called decomposers.
They release digestive enzymes to break down
organic matter and then absorb the products
of digestion.
Decomposers include fungi and bacteria.
Decomposers do not fit readily into one trophic
level.
So where does all the energy go if not 100% from one organism to the next???
Energy losses in food chains
1. Some parts of the organism not eaten
2. Some parts are not eaten but cannot be digested and are therefore lost in feaces
3. Some of the energy is lost in excretory materials, such as urine
4. Some energy losses occur as heat from respiration and directly from the body to the environment.
Why would energy losses be higher in birds and mammals compared to reptiles/amphibians?
Stoat
Toad
Caterpillar
Grass
1. Limits to 4/5 organisms because insufficient energy is available to support a large enough breeding population at trophic levels higher than these
2. Total mass of organisms in a particular place (biomass) is less at higher trophic levels
3. Total amount of energy stored is less at each level as one moves op a food chain
How does the relative inefficiency of energy transfer between trophic levels affect food chains?
Trophic level
