1. Ecosystems: food chains and food webs
Section 5

2. Ecosystems
Groups of living and non-living things (the environment they live in) make up an ecosystem
Some ecosystems include forests, ponds, and streams
There are lots of different components that make up an ecosystem. These are the communities, habitats and populations

3. Habitat A habitat is a place where an organism lives
E.g. A fishes' habitat could be pond water
A habitat is a component of an ecosystem

4. Population & Community
A population is a group of the same species that live in a habitat
A community is the sum total of all the populations of plants, animals and micro- organisms living together in an ecosystem

5. This entire picture represents a pond ecosystem.
The pond is a habitat
All the organisms of the pond make up the pond community
All the organisms
of one kind make
up a population

6. Producers and Consumers
All living things gain energy from the sun
Green plants can photosynthesise and therefore make their own food so are called producers
Animals and non-green plants have to consume other animals and plants to gain energy to stay alive and grow. They are known as consumers
Produces its own food to gain energy
Consumes other animals to gain energy

7. Producers and Consumers
Among animals, there are different types of consumer:
Ones that eat only plants – HERBIVORES
Ones that eat only other animals – CARNIVORES
Ones that eat both plants and animals - OMNIVORES

8. Predators and Prey
An animal which hunts another animal for its food is called a predator
The hunted animal is called the prey

9. Decomposers
An important groups of organisms in an ecosystem are decomposers because they break down the dead remains of animals and plants.
Decomposers play an important role in recycling of nutrients
Fungi and bacteria are important in the decomposition process

11. Niche A niche is the role an organism plays within a habitat
E.g. The niche of a decomposer is to recycle nutrients from dead organisms, the niche of a green plant is to produce food for other organisms as well as themselves

12. Niches
The niche of a species is its role in its habitat

13. Task
Make a table with the headings “Organism from Loch Ecosystem” and “Description of Niche”
Using the diagram on the previous slide, write down the organism and describe its niche in the ecosystem

14. Organism from Loch Ecosystem
Niches
Organism from Loch Ecosystem
Description of Niche
Minute Green Algae
Microscopic floating producer
Bacteria
Decomposer
Lice
Parasite feeding on fish scales
Water flea
Small swimming herbivore
Osprey
fish-eating bird of prey
Brown Trout
Medium-sized swimming carnivore
Pondweed
Rooted underwater producer
Pike
Large predatory swimming top carnivore

15. Food Chains
When an organism eats another organism, energy is being transferred
This transfer of energy can be represented as a food chain
The arrows indicate the direction of energy flow

16. Food Chains Food chains always start with producers
A herbivore which eats plants is known as a primary consumer in a food chain
An animal which eats the primary consumer is known as a secondary consumer and so on
Remember, the arrows indicate that energy is being transferred from one organism to the next

18. Producers & Concumers
cience/living_things/food_chains/play.shtml

19. Food Webs
Food chains are linked together in a complex way to form food webs
Under natural conditions, an ecosystem really contains many inter-connecting food chains

20. Quiz What is a producer? What is a herbivore?
What is a secondary consumer?
What is meant by the terms predator and prey?
What might happen to the population of rabbits in a food chain if foxes were removed?
What do arrows in a food chain represent?

21. Answers
A producers is a green plant that makes its own food by photosynthesis
A herbivore is an animal that only eats plants
A secondary consumer is an animal that eats primary consumers
A predator is an animal that kills other animals for food. A prey is an animal that is hunted for food.
If foxes were removed, the population of rabbits would increase (because there are no predators)
Arrows in a food chain indicate the direction of energy flow

22. Energy Loss
As energy flows through a food chain or web, energy is lost at every stage
Energy is lost in a number of ways:
Movement of an organism will generate heat energy which is lost
Expelling wastes e.g. Faeces which contain undigested food
Only 10% of the energy in a living organism is passed on to the next animal in a food chain because of these reasons

23. Summary of Energy Loss
2. Some of the energy in the leaf is lost in waste which passes through the digestive system of the caterpillar
1. The caterpillar eats the leaf
3. Some of the energy is lost as heat as the caterpillar moves about
4. Only a small proportion of the energy is stored in the body of the caterpillar. This is the only energy available to the animal that eats it

24. Pyramids of Numbers
Loss of energy from a food chain usually means that the organisms nearer the top of the food chain are fewer because there is less energy to support a large population
A pyramid of numbers is a diagram which represents the number of organisms at each stage in a food chain as a horizontal bar in pyramid- shaped bar chart

25. Pyramids of Numbers
Pyramids of Numbers do not always have the same shape
One organism can have more energy than 10 organisms at the next level
e.g. ONE oak tree has more energy than 100 caterpillars
Grassland
Habitat
Woodland

26. Pyramids of Biomass
A pyramid of biomass is a diagram which represents the total mass of organisms at each stage in a food chain as a horizontal bar in a pyramid-shaped bar chart
Remember that biomass is not always related to the number of organisms!
There maybe one organism with a large mass that can pass on energy to a large number of consumers

27. Pyramids of Biomass

28. Pyramids of Energy Pyramids of Energy
Diagrams that represent the quantity of energy at each stage in a food chain as a horizontal bar in a pyramid-shaped bar chart
Secondary Consumer
Primary consumer
Producer

29. Pyramids of Energy
As energy is always lost at each stage, so the shape of a pyramid of energy is always maintained

30. Quiz
Which of the pyramids of numbers shown is the best representation of a food chain that starts with an oak tree and ends with hawk?
Why are there rarely more than four or five links in a food chain?
Describe two ways in which energy is lost from a food chain C A B

31. Answers B
Because so much energy is lost at each step there is not enough to sustain more links
As heat and as waste such as faeces and urine

32. Variety of Species
Organisms that belong to the same species can breed with one another to produce fertile offspring
This means that when offspring reach sexual maturity, they will be able to produce more offspring themselves

33. Animals belonging to the same species can interbreed to produce fertile offspring
Animals that do not belong to the same species produce infertile offspring

34. examples
X =
X =

35. Biodiversity
Biodiversity means the variety of species present in an ecosystem’s community
There can be biodiversity between members of the same species and between different species
Bio = living, Diversity = differences
Biodiversity = differences in living things

36. Stable Ecosystems
Which of these ecosystems is stable and which is not? Give a reason for your answer.

37. Stable Ecosystems
Stable ecosystems contain a variety of species and can last a very long time
If there are only a few species within an ecosystem, any change in population will severely affect other populations

38. Adaptations and Distribution
An adaptation is a feature of an organism which enables it to survive successfully in its habitat
The adaptations of an organism can dictate where that organism lives and what it eats in the case of animals
Two examples of organisms that have adapted to suit their environments are a type of bird called the finch and cactus plants

39. Adaptations and Distribution - Finches
Charles Darwin visited the Galapagos Islands and recorded his findings about the different species of finch.
He found that:
On each Island, the landscape and food source for the finches was different
The finches had adapted to their environment by changing their body size and beak shape so that they could eat food and survive
This resulted in 13 different species being formed over millions of years

41. Adaptations and Distribution
Adaptation of nectar-eating Ground Finch – it has a long, thin beak to get nectar from flowers
The distribution of Woodpecker Finches is restricted to trees as this is were its food source is
The seed-eating Ground Finch cannot survive on an island which has few trees and shrubs because its beak is adapted to eat this type of food only

42. Beak Adaptations Experiment
In your notebook, write a short report to summarise your finding from the experiment. You can work in a group or with a partner if you wish.
Here is some information that you may want to think about:
Describe how different “beak” types are suited to different food sources and say why.
Which “beak” types were the most successful and why?
Which “beak” types were the least successful and why?
What will happen to the populations of the most and least successful beak types? Again, say why this is.

43. Adaptations in Cactus Plants
The desert is a hot, dry environment where water is in limited supply
Cactus plants have adapted to this environment by employing the following mechanisms:
Leaves have been reduced to spines to limit water loss via evaporation because of the smaller surface area
Root network is extensive to absorb water when it does rain
The green stem of the plant has a thick, waxy cuticle to reduce water loss
The stems and leaves are succulent and fleshy to store water

45. Habitat Destruction - Grazing
Animals that graze on plant species help to keep ones that show vigorous growth in check (this means one species of plant will not take over all the others)
If grazing is at a very high or low intensity, this can affect biodiversity as some plant species may disappear or one species may overtake the rest

46. Habitat Destruction – Effects of Human Activity
Sulphur Dioxide
Burning fossil fuels and emissions from car exhausts release sulphur dioxide into the atmosphere which can damage many types of plants
Acid Rain
When acid rain falls, it lowers the pH of soil and rivers and organisms die as a result

47. Thermal Pollution
on?quick=v4#
When water used as a coolant, it is returned to the natural environment at a higher temperature and the change in temperature impacts organisms by
(a) decreasing oxygen supply
(b) affecting ecosystem composition

48. Habitat Destruction – Effects of Human Activity
Deforestation
Huge forests of South America are being cut down at an alarming rate. This reduces biodiversity and has many other impacts of Earth, including climate change
Deforestation in the Amazon

49. Competition In Animals
Where resources are limited, animals compete with one another, even members of the same species
Animals will compete for:
Food
Water
Shelter
Mates
Evolution ensures that only the best adapted animals (and plants) will go on to reproduce and pass on these desired traits

50. Competition In Plants Plants compete for the following resources:
Water
Light
Space to grow
Nutrients for strength and proper development

51. Behaviour
All animals, no matter how simple, show adaptations to their environment. This is normally a response that ensures well-being and survival
Changes in the surrounding environment to which an organism is sensitive to can be described as an environmental stimulus
The response by the organism to the stimulus is a behavioural response

52. Woodlice
When in dry environments, their rate of movement will increase
When they enter a damp environment their rate of movement slows down
This response ensures that they do not dry out and die

53. Swallows and Length of Day
As the day length decreases in the autumn, swallows respond by migrating south to Africa
This is because the insects that swallows feed on are more readily available in Africa in the winter

54. Sea Anemones Found attached to rock surfaces in rock pool
They have tentacles which pull things towards their bodies if these objects touch them
Mechanism for catching prey

55. Survival Value
Responses to the environment are often very useful and offer a survival advantage
E.g. avoids predators, catching prey, ensuring favourable conditions for biological processes

56. Investigating Woodlouse Behaviour
Found beneath leaf litter, stones and dead bark
Damp conditions protect from predators and from drying out
Woodlice are studied because of simple behavioural patterns and apparatus used

57. Experiment Collect 10 woodlice per group
Introduce woodlice into the choice chamber through the hole - gently!
After 10 minutes, record how many woodlice are on each side of the choice chamber (light or dark side)
Using class results, work out a class average for the number of woodlice on each side of the chamber

58. Reliability and Validity
In your experiments, it is important that more than one woodlouse was used to ensure that the results are reliable
If the humidity and light were both changed in each chamber then the results of an experiment would be invalid as more than one factor is being changed so you cannot reliably say what has caused the woodlice to move

59. Quiz
A choice chamber is set up with one side moist and the other side dry. Ten woodlice are placed in the choice chamber and left for 1 hour undisturbed.
Where should the woodlice be placed?
Why are ten woodlice used rather than one?
State two factors that should be kept constant during the investigation
Where would you expert to find the woodlice at the end of the investigation?
What advantage is it to the woodlice to behave in this way?

60. Answers In the middle or equal number on each side
To improve reliability
Temperature and light intensity
On the moist side
They reduce water loss from their bodies