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IGCSE Unit 20 Organisms and their environment

Updated to follow Mary and Geoff Jones Cambridge IGCSE Biology Coursebook 3rd edition. Follows Co-ordinated sciences syllabus
by

Blanca Peris

on 6 March 2017

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Transcript of IGCSE Unit 20 Organisms and their environment

CHAPTER 20:
ORGANISMS AND THEIR ENVIRONMENT

A pyramid of NUMBERS represents the
relative number
of organisms at each trophic level
Energy transformations are never 100% efficient, usually 10-20%.
Feed on producers.
Trophic level:
the position that an organism occupies in a food chain
/
web
Population:
a group of organisms of the same species who live in the same area at the same time.


Community:
a group of populations living and interacting with each other in an area.


Ecosystem:
a community and its abiotic (non-biological) environment. It is considered a unit containing all of the organisms and their environment, interacting together, in a given area.
A pyramid of BIOMASS represents the
mass
of living organisms being considered at each trophic level.
The energy is released by cell respiration and lost as heat.
Primary consumers obtain energy from eating producers.
Light from the Sun is the initial energy source for almost all communities.
Food web diagrams are very complex and show interactions between species within a community.
Secondary and tertiary consumers:
Energy is transferred through a series of organisms, each feeding on the preceding.
 20.2 KEY DEFINITIONS
FOOD WEB
20.1 INTRODUCTION
Ecology:
the study of relationships between living organisms and between organisms and their environment.
 25.2 KEY DEFINITIONS
Producer:
organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis.
Food chain:
chart showing the flow of energy from one organism to the next beginning with a producer.
Food web:
network of interconnected food chains showing the energy flow through part of an ecosystem
=Ecosystem
20.3 ENERGY LOSSES BETWEEN TROPHIC LEVELS
Mainly green plants and algae in aquatic ecosystems
Organism that gets its energy from dead or waste organic matter.
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/interdependence/adaptationsact.shtml
Adaptation
Video
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/energy_biomass/energyinbiomassact.shtml
Energy losses in producers
Energy losses in consumers
Energy losses in decomposers
20.4 PYRAMID OF NUMBERS, BIOMASS AND ENERGY
The shape is due to less energy flowing through the food chain as energy is lost by each trophic level so they usually have fewer than five trophic levels.
20.5 THE CARBON CYCLE
20.1 INTRODUCTION
 20.2 KEY DEFINITIONS
20.3 ENERGY LOSSES BETWEEN TROPHIC LEVELS
20.4 PYRAMID OF NUMBERS, BIOMASS AND ENERGY
20.5 THE CARBON CYCLE
Carbon is an extremely important element.
20.6 EFFECTS OF THE COMBUSTION OF FOSSIL FUELS AND THE CUTTING DOWN OF FORESTS ON THE O AND CO CONCENTRATIONS IN THE ATMOSPHERE
2
2
20.6 EFFECTS OF THE COMBUSTION OF FOSSIL FUELS AND THE CUTTING DOWN OF FORESTS ON THE O AND CO CONCENTRATIONS IN THE ATMOSPHERE
2
2
When you burn a fossil fuel (hydrocarbon + oxygen) carbon dioxide and water are produced.
A pyramid of ENERGY represents relationships between organisms in different trophic levels. Advantages:
- Comparisons based on biomass may be misleading as two species do not necessarily have the same energy content.

20.4 PYRAMID OF NUMBERS, BIOMASS AND ENERGY
Habitat:
the environment in which a species normally lives OR the location of a living organism.
Species:
a group of organisms which can interbreed and produce fertile offspring.
• carnivore as an animal that gets its energy by eating other animals.
• herbivore as an animal that gets its energy by eating plants,
Consumer:
organism that gets its energy by feeding on other organisms,
The Sun is the principal source of energy.
Energy loss
limits the length of food chains. Heat loss in transfer is not recycled.
A food web can show:
1) more than one producer supporting a community
Food web vs food chain
Food web vs food chain
3) a consumer with different food sources on the same or different trophic levels
2) a single producer being a food source for a number of primary consumers
A group of organisms in a community that occupy the same position in food chains.
OR
The first trophic level is occupied by the producers.
20.3 ENERGY LOSSES BETWEEN TROPHIC LEVELS
The third level are secondary consumers, and those of the fourth level are tertiary consumers.
The organisms of the second trophic level are the primary consumers;
Producers
Primary consumers
Primary consumers also include parasites (fungi, plants or animals) of plants.
In aquatic ecosystems: small crustaceans and molluscs.
On land: insects, reptiles, birds as well as mammals.
They may be predators, which hunt, capture and kill their prey;
Tertiary consumers feed on secondary consumers.
Feed on primary consumers.
Or parasites, in which case they are smaller than their hosts are.
Decomposition helps in:
The reduction of high energy carbon compounds.
The recycling of nutrients stored in the organic materials
The formation of soil.
Decomposers
These materials are decomposed by fungi and bacteria.
When plants and animals die their bodies still contain energy and raw materials, as do the waste products such as urine and faeces.
Only a small proportion of the incoming energy (1-2%) enters the ecosystem.
release energy by cell respiration for use in the producer then loss as heat
death of the producer and energy passes to decomposers when they digest it.
energy passes to a primary consumer when it eats the producer
This energy trapped by the producers eventually leaves them in one of three ways:
As heat.
As some organic matter is not digested some energy is lost in faeces and passes to decomposers.
The energy they take leaves them in one of three ways:
To decomposers when primary consumer dies or parts are left uneaten.
To a secondary consumer when if they are eaten.
- Each bar represents the amount of energy per unit area or volume.
- They are the most useful but they are the most difficult to obtain data for.
20.5 THE CARBON CYCLE
Respiration and burning fuels releases carbon into the atmosphere as carbon dioxide.
Plants get their carbon from carbon dioxide in the atmosphere and animals get their carbon from plants when feed on them.
When the organism dies, they are eaten by decomposers and the carbon they receive is released back into the atmosphere.
Photosynthesis consumes carbon dioxide and water to produce oxygen and glucose.
Hence, combustion of fossil fuels will decrease the oxygen concentration and increase the carbon dioxide concentration.
Cutting trees down will increase the carbon dioxide concentration and decrease the oxygen concentration.
THE END
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