Ecology and the Environment

Section 4: Ecology and the environment

a) The organism in the environment

Students will be assessed on their ability to:

4.1 understand the terms population, community, habitat and ecosystem

4.2 recall the use of quadrats to estimate the population size of an organism in two different areas

4.3 describe the use of quadrats as a technique for sampling the distribution of organisms in their habitats.

b) Feeding relationships

Students will be assessed on their ability to:

4.4 recall the names given to different trophic levels to include producers, primary, secondary and tertiary consumers and decomposers

4.5 understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer

4.6 understand the transfer of substances and of energy along a food chain

4.7 explain why about only 10% of energy is transferred from one trophic level to the next.

Key words

Producer Consumer Primary

Secondary Tertiary Pyramids

Numbers Biomass Energy

10 February 2015

How can we use this quadrat to learn about the type of plants and the distribution?

animation

Food chains

• http://www.youtube.com/watch?v=TE6wqG4nb3

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Consumers can be grouped into different types:

CarnivoresThese consumers eat other consumers. They eat animals.

Herbivores These consumers eat producers. This means plants and possibly bacteria.

OmnivoresThese consumers eat other consumers and producers. They eat animals and plants. Most humans are omnivores.

Feeding types

What is the food chain in this habitat?

Copy the food chain and add the following labels.Producer Primary consumer Tertiary consumer Herbivore Secondary consumer Sun Carnivore

Copy the food chains and then label the rank of the consumers

blue tit

chiffchaff

aphid

moth larva

vole

stoat

owl

spider

ladybird

plants

Questions

1. Explain what the arrows in the food chain represent?

2. Not all energy is passed from one level to the next. Explain how it can be lost along the way.

Thinking time

• How many zebra do you think a lion eats in a

month?

• How many grass plants do you think a zebra

eats in a month?

Pyramid of numbers

• The arrows in a food chain show the flow of energy

• In a day, one crab would eat more than one mussel, and

each mussel would eat more than one seaweed plant

Seaweed Mussels Crab

• If you count the number of crabs, mussels and seaweed

plants you can draw a scale diagram. You can represent

the size of a population by a bar

SEAWEED

MUSSELS

CRABS

Draw pyramids of numbers using a scale for the following

food chains

Tertiary 1 cat 100 fleas

Consumer

Secondary 5 thrushes 5 robins

consumer

Primary 20 slugs 100 caterpillars

consumer

Producer 5 cabbages 1 oak tree

Questions

Draw the following pyramids of numbers to scale on graph paper.

15 nettle plants 12 caterpillars 1

robin

5 rose bushes 100 greenfly 25

ladybirds

50 lettuce 20 slugs 1 thrush

Pyramid of numbers

• The size of each block represents the number of organisms

• Each level in the pyramid represents a trophic level

• Has its shape because there is less energy available as you go up the trophic levels therefore there are fewer organisms at each level

InterdependenceMake 5 correct sentences by choosing a word or

phrase from each column

A food chain

A food web

A pyramid of numbers

shows how food chains

energy flows

many

organisms

depend on each other for energy

link to each other

from one organism to another

organisms there are at each stage in the food chain

You have 30 seconds to talk through this diagram

• Plants utilise only about 1 percent of the energy the earth receives from the sun.

• Where does the other energy go? , make a list where you think it goes.

Starter

Efficiency

Energy Transfers

• Energy comes into an ecosystem from sunlight and is fixed by plants by photosynthesis.

• There is another process called chemosynthesis (involves bacteria).

• The energy stored in the plants can be passed onto other organisms along food chains.

• Each link in a food chain is called a trophic level.

• During this process a lot of energy is lost – dissipation.

Key Points

• Plants are not very efficient at capturing energy from the sun.

• The products of photosynthesis can be used to increase the biomass of plants.

• This biomass can be eaten by herbivores

• Most of the biomass eaten by the primary consumer is used in respiration to– Move

– Maintain body temperature

Key points

• Some biomass will be undigested and pass through the animal without being used.

• The only biomass available to consumers at the next level is that that is used for growth.

• This process happens at each trophic level in the pyramids of biomass– There is less and less biomass available at each

subsequent level.

• The energy in all ecosystems originally come from the sun.

• Most of the sunlight that falls on leaves is not absorbed and used.

• Some is reflected by the leafs surface.

• Some passes through the leaf.

• Only part of the light is useful and can be absorbed by the chlorophyll.

You have 30 seconds to talk through this diagram

• Transfer of food energy from producers to primary consumers also involves wastage.

• For every 100g of plant material available only about 10g ends up as part of the herbivores body.

• Reasons for 90% energy wastage:

• Some food may not be eaten.

• Some food passes through the body of the herbivore without being digested.

Energy flow through consumers

• A lot of food is used in respiration.

• Similar losses in food energy occur between other trophic levels.

• Some carnivores are able to achieve a 20% conversion effeincey. So for every 100g of herbivore that they eat 20g ends up as part of their body.

Pyramids of biomass

• The mass of living things at each stage in the food chain

• Measured in dry mass

• The size of each box represents the mass of each kind of organism

• Always makes a pyramid shape (a pyramid of numbers can be upside down)

Difficulties with food pyramids

• Many organisms eat lots of things• Could be at different levels

• Calculating dry mass involves killing and drying

organisms

Numbers or Biomass?

Plenary

• Pyramids of numbers tell us the number of

predators-prey at each feeding level, however,

they do not give a very good indication of the

energy transferred.

• Can you think of a better way of measuring how

much energy is transferred between stages in

the food chains? What other quantity could we

use in a pyramid instead of number of

animals/plants?

Food chains

• http://www.youtube.com/watch?v=TE6wqG4nb3

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1. Give three ways in which fish are adapted to live

underwater.

2. Explain how a polar bear is adapted to its

environment.

3. Explain how a camel is adapted to its environment.

Extension: How is a tree adapted to its environment?

Life on land - Mammals

What features does a mammal have?

Warm bloodFur

LungsGives birth to live young

Produces milk

What adaptations do you think mammals have to be able to

survive in:1. Desert conditions2. Arctic conditions

Life in water - Fish

How is a fish adapted to live in

water?

• Think about its shape, how it moves through the water.

• How does it get oxygen?

• What protects it from skin infections?

Adaptation and competition

• Animals, plants and other organisms are adapted to their environment.

• Where there are limited resources, individuals must compete for resources.

• Individuals that are unable to compete will die out and not pass their genes onto the next generation.

Exponential growth

• When resources are unlimited, the population will grow

The population will double in every period of time

Time

Num

ber

of

indiv

idual

s

T1 T2 T3 T4

10

100

1000

1 ???

Limited resources

Competition between individuals

• The population is limited by the

amount of resources

• Strongest individuals survive to the

next generation

Competing for resources

List the resources that each of the following compete

for:

•Animals

• Plants

When limits are reached

Num

ber

of

indiv

idual

s

T1 T2 T3 T410

100

1000

1 ???

Num

ber

of

indiv

idual

sT1 T2 T3 T4

10100

1000

1 ???

Population CrashPopulation growth limited

Lynx and Snowshoe Hare Pop. Data (n x 1000)

Year Lynx Hare

1845 30 20

1850 10 80

1855 35 82

1860 10 15

1865 75 130

1870 55 100

1875 20 15

1880 84 135

1885 20 40

1890 58 82

1895 63 65

1900 5 40

1905 52 10

1910 12 85

1915 62 5

Plot a graph of year against

population. Plot lynx in one

colour and hare in another.

1. What is the relationship between

number of lynx and number of

hare?

2. Explain why this happens.

3. Extension: Which is the predator?

How can you tell from the graph?

Lynx and Snowshoe Hare Pop. Data (n x 1000)

Year Lynx Hare

1845 30 20

1850 10 80

1855 35 82

1860 10 15

1865 75 130

1870 55 100

1875 20 15

1880 84 135

1885 20 40

1890 58 82

1895 63 65

1900 5 40

1905 52 10

1910 12 85

1915 62 5

Plot a graph of year against

population. Plot lynx in one

colour and hare in another.

1. What is the relationship between

number of lynx and number of

hare?

2. Explain why this happens.

3. Extension: Which is the predator?

How can you tell from the graph?