This document provides an overview of key concepts related to ecosystems, including definitions of ecosystem, population, community, habitat, trophic levels, food chains, food webs, biomass, energy pyramids, and decomposers. It also discusses how energy is lost at each trophic level as it is transferred between organisms, limiting the length and productivity of food chains. The learning outcomes indicate students should be able to define important terms, draw and label a food web, discuss food pyramids and energy transfer, and explain biomass and its role in ecosystems.

1. Life science
Grade 10
Ecosystem

2. 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.

3. ECOSYSTEMS
An ECOSYSTEM is all the different organisms in
the world living together in a PARTICULAR
ENVIRONMENT
or HABITAT
Our own bodies are homes to tiny
living organisms!
All the ecosystems combined together make up the BIOSPHERE

4. 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.

5. Ecosystem
 The collection of organisms in
an area along with the
important environmental factors
 Eg ocean ecosystem

6. An example ecosystem

7. Population
 A population is the number of
organisms of the same species
living in a habitat

8. Community
All the animals and plants
living in an ecosystem

9. Habitat
 The area where animals and
plants live
 Eg ocean habitat
 Or.. More specific Coral
habitat

10. Trophic levels
The level occupied by a consumer in a food
chain is referred to as a feeding or TROPHIC
level.
Primary consumers occupy the 1st trophic
level; secondary consumers occupy the 2nd
trophic level, and so on.

11. 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

12. Producer
Primary Consumer
Herbivore
Secondary Consumer
Carnivore
Tertiary Consumer
Carnivore

13. What happens if a link in the food chain is broken?
X
X

14. Food webs
The interrelationship between many food chains
is called a food web.

15. Biomass
Biomass 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.

16. Pyramid of Biomass
The base of the pyramid
represents the matter in
producers. The next
level shows biomass of
primary consumers and
so on….

17. 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.

19. Energy pyramid

20. Decomposers
Organisms 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.

21. So where does all the
energy go if not 100%
from one organism to
the next???

22. 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?

23. Energy transfer in ecosystems

24. 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