The Biosphere

Investigating an Ecosystem

Ecosystem

Made up of living and non living parts

POND

WOODLAND

SOIL

MOOR

Abiotic

Food availability

Predation

Temperature

Light intensity

Moisture

Biotic

QuadratEstimates the abundance of non moving organisms

Throw randomly

Count the number of squares an organism is found in

Errors ?Non random throwing

Counting the same organism over two squares

Too few quadrats done

LMMCan measure both light intensity and moisture content of a particular area

Errors ?

Shadow

Read wrong scale

Stone Too few readings

Pitfall Trap

Alcohol (if you The samples Killed)

Pitfall Trap

More

Results Quadrat 1 2 3 4 5 6 7 8 9 10

Light Intensity A B C D E F G H H H

Soil moisture 3 2 3 1 4 3 2 3 4 3

grass 6 8 8 10 15 20 23 25 25 25

Daisies 0 0 0 0 5 11 16 19 22 22

Sorrel 20 15 15 10 10 5 0 0 0 0

Tullgren

Ecosystems and Energy Flow

3

What is an ecosystem?

An ecosystem is all the animals and the plants in a habitat, together with their environment.An ecosystem provides everything that the animals and plants that live there need.A rock pool is an ecosystem, and so is a forest or a lake.

Ecosystems

Made up of a number of different habitats sharing the same environment. E.g. a desert.Habitat - a place where living things live.

E.g. a pond.Community - a group of populations

living in a habitat.Population - a group of organisms of the

same species.

What is a habitat ?

A habitat is the place where living things live.

It is more than just a home it includes the whole surrounding area.

The habitat provides the animal or plant with food or shelter.

People and their habitats People can live all over the

world.

We can do this because we are able to build homes for different conditions.

Also we can change our Also we can change our clothes to best suit the clothes to best suit the temperature around us.temperature around us.

White clothes reflect the heat

Animal skin and fur act as insulators and keep heat in.

Animals and plants

Most plants and animals are specially adapted to survive in a particular habitat.

They have developed special features to suit the demands of their environment.

This is called adaption.

Some examples of adaption

All birds have similar characteristics.

But many water birds have features that are different from those birds live on land.

Long legs are good for wading

These wings act as flippers

Webbed feet for swimming

Some animals are camouflaged to blend in with their surroundings.

This keeps them safe as it is more difficult for other animals to see them or catch them for food.

This lizards skin is so similar to the rock colour.

These zebra could easily be mistaken for bushes from a distance.

This lion blends in well with the grassy background.

Aquatic animals have streamlined bodies to move more easliy in the water.

These animals have adapted to live in the hot climate of the desert.

Camels store water in their humps.

Ostriches have long eyelashes to keep out the sand.

Snakes glide across the hot sands and can shed their skin

These animals have adapted to be more suited to cold temperatures.

Layers of fat keep the seals body warm, and small ears stop heat loss.

Polar bears are kept warm by their body fat.

Deer have a warm layer of fur.

How do changes in the environment affect

organisms?

Living things are adapted to daily changes in their

habitat…………….

Daily changes

Flowers open and close

Daily changes

Sea anemones pull in their tentacles when the tide goes out to stop them drying out.

Living things are adapted to seasonal changes in their

habitat

Seasonal changes in a garden

A garden in the summer

A woodland

A woodland in spring

The Arctic

The Seashore

Some plants store their food for winter underground in

their roots and stems.

Squirrels store foods like nuts in the autumn to eat during the winter when there is not much food around.

Some animals like tortoises, hedgehogs and bears, cannot store food to keep them warm. Instead they go to sleep in a warm sheltered place, such as under pile of old leaves or inside an old tree trunk. This is called hibernation.

Energy Flow in a Habitat

Plants trap energy converting it to

biomass.Producers

Plant biomass eaten by animals

Primary Consumers

Larger animals eat animals that eat

plantsSecondary Consumers

All energy initially comes from the sun as light energy

Terminology to Learn

Herbivore - animals that eat only plants.Carnivore - animals that eat only animals.Omnivore - animals that eat plants and animals.Top Carnivore - animals not eaten by anything else.Decomposer - organisms that live on dead material.Trophic Levels - each step along a food chain.

Trophic levels

What does this food chain show?

The plant is eaten by the slug.The slug is eaten by the frog.The frog is eaten by the heron.

Food Web

Write out four food chains found in the food web.

How do Organisms Interact?

•What happens to the locust population if the slugs die out?•What happens to the plant population?

Pyramid of Numbers

This is another way of showing a food chain.

5000 Dandelions 100 Rabbits 1 Fox

1000 Pea Pods 100 Slugs 10 Frogs 1 Bird

•Why do the numbers drop as you go up the trophic levels?•Draw the pyramid of numbers for these food chains.

Pyramids of Numbers - examples

5000 Dandelions

100 Rabbits

1000 Pea Pods

100 Slugs

10 Frogs1 Fox

1 Bird

Pyramid of Numbers

1 Pear Tree

3000 Greenfly

1000 Ladybirds

1 Partridge

5000 Dandelions 100 Rabbits 1 Fox 500 Fleas

Now draw the pyramids of numbers for these food chains.

Pyramids of Numbers - examples 2

5000 Dandelions

100 Rabbits 3000 Greenfly

1000 Ladybirds

500 Fleas

1 Tree

1 Partridge

1 Fox

Pyramid of BiomassBiomass is how much dry mass is present in each trophic level. For this reason Biomass Pyramids always look the same.

Energy flow

Each animal in the food chain eats another animal or a plant in order to gain energy.The energy flow in the ecosystem keeps all of the animals alive.

Pyramid of Energy transfer

Where does the energy come from?

The SunIn every ecosystem, Energy is trapped and

stored by the plants (primary producers).Some energy is always lost in the transfer

of energy between trophic levelsEcologists have calculated 10% of energy

available in a trophic level is taken up by the level above

Energy flow in a food chain

Sun 98% energy lost

Producer 90% energy lost

Primary consumer 90% energy lost

Secondary consumer 90% energy

lostTertiary consumer

Energy flow through Producers

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

What happens?Some is reflected from

the leaf’s surfaceSome passes straight

through the leafOnly part of the light is

useful and can be absorbed by chlorophyll

The overall efficiency of energy transfer during photosynthesis is less than 10%

So only about 8% of sunlight energy reaching the plant is transferred into useful chemical energy.

What is this chemical energy used for?

For respiration and growth

When the plant grows, its biomass will increase. This will provide food energy for herbivores.

It may be transferred between trophic levels from producers to primary consumers.

Some food energy may be transferred to decomposers.

When leaves are shed, fruit and seeds are dispersed and when the plant itself dies.

Decomposers eat the dead plant tissues to get energy.

Energy flow through a green plant

Released in primaryRespiration consumers

Producer decomposers

energy inputSUN

What happens

to the other 90%?

Only 10% of the stored energy in the deer is transferred to the lion

Write down what happens to the missing 90% of the energy in a

deer ( Kudu) that is not transferred to the lion.

What are the units?

kJ/m²/yrUnit of energy/ area/time(kilo Joules per metre squared per

year.)

Important to remember that pyramids of energy transfer are NEVER inverted.

The reasons for the inefficiency of this energy

transfer are:-

Some plant material passes out of the body of the herbivore as faeces without being digested.A lot of energy is used in respiration.Some energy passes to decomposers in dead remains.

Carnivores are able to achieve 20% efficiency.

Why?

20% of the herbivores biomass ends up as the carnivores biomass.

This is possible because proteins are more efficiently digested than are carbohydrates.

Energy Flow in a food chain

Some people eat kudu.What is the food chain?

Grass Kudu humanOf the 1000 000kJ of Energy which falls on one square metre of grass in a year only 100kJ available for humans.

Where does all the energy go?

Plants convert a small % of light energy into glucose (biomass)’The energy works its way through the food chain,but trophic level 2 only takes 10% of total energy of trophic level 1The 90% of energy lost is used in staying alive: –HEAT

–Excretory products

This explains why pyramids of biomass get smaller as they go up and why food chains are rarely more than 4 links long.

–movement–life processes

Match the words and phrases.

A food chain showsMost food

chains start withPlants are

Animals are

Animals that hunt and eat others are calledAnimals that are caught

and eaten are called

producers

consumers

predatorsprey

a green plant

what is eaten by what

A population is a group of organisms of the same species living in the same place at the same timeMillions of different populations all evolving according to their own self interest in a particular environment. But each population is a part of the environment of its neighbors, so any evolutionary change has a ripple effect.

Properties of populations

•Birth rate; count number of live births in a given period.

•Death rate; count number of deaths in a given time period.

•Growth rate; balance between birth/death rate. For population to grow, birth rate must exceed death rate.

•Age structure, Density,and dispersion are also factors

A population is a group of organisms of the same species living in the same place at the same time

The growth rate of a population is the increase in the number of individuals over time.

Exponential growth is when the number of individuals grows at a constant rate. Growing bacteria in a lab is a good example

Generation # of bacteria time1 1 02 2 15min3 4 30min4 8 45min5 16 1hr6 32 75min7 64 90min8 128 105min9 256 2hrs10 51211 102412 204813 4096 3hrs14 819215 16,38416 32,76817 65,536 4hrs18 131,07219 262,14420 524,28821 1,048,576 5hrs

But can a population continue to grow at this rate? NO

Limiting factors will control population growth

•Food shortages

•Lack of space

•Accumulation of own waste products

•Lack of other resources like oxygen, living space etc.

A PopulationGroup of organisms of the same species living in the same place at the same timeIndividuals may come and go, but the population can remain the sameThe Nakuru Flamingos each year, for Example

Population GrowthSince each organism of a population is governed by the selfish gene, populations tend to grow.If unlimited resources are present, growth will be exponentialIt will proceed very quickly for rapidly reproducing organisms and more slowly for slowly reproducing onesThe curve, however, will always be a “J” curve or an exponential growth curve

Population Growth 2Resources are never unlimited, though. As population rises, resources decline.If the growth is too rapid, resources are rapidly depleted and a population crash can occurThis pattern occurs often with many populations (including humans)For example...

Gypsy moth caterpillar

Population Growth 3More often what happens is that the resources slowly decrease, the growth rate slowly decreases, and they meet.This point that they oscillate around is the carrying capacity of the environment for that particular organismSo when would you “harvest” these individuals? (1,2,3,4,or 5)

S - shaped curve

Growth Rate Limiting Factors

(affecting birth or mortality rates)

Predation Increased

competition for scarce resources

Sickness Others?...

Weather Ice Age Global Warming Flood El Nino Etc.

Range of tolerance of environmental conditions is an important factor:

temperature, light, salinity, nutrients, water etc

Predator-Prey Cycles

Control of Population Size

Lynx

Snowshoe Hare

Lynx cycle lags behind hare by 1-2 yrs.

Why?

What is the cause of these population changes?

When hare numbers increase, 2 things happen:

1. Shortage of food for hares 2. Increase in Lynx number (predation)

Lynx numbers increase when Hare numbers high, but if food for hares is low and predation is high……………………..

…………soon the Hare population will crash (drop).

(1) Some Lynxes leave (emigrate) to where food is more plentiful.

(2) Lynxes eat other prey when hare numbers low.

(3) More competition between Lynxes.

A CRASH in the Lynx population

This drop in Hare numbers leads to 3 things …

Lower Hare numbers – vegetation starts to grow again

+ Hares have fewer Lynx to watch out for

+ There is more vegetation to eat

SO, the number of Hares begins to increase

The PREDATOR PREY cycle begins again

MEANWHILE…..

Highest peaks always belong to PREY

Why?The predator is ALWAYS at a higher level in the pyramid of numbersThan the prey, so the numbers of prey are always HIGHER than predators

COMPETITION…

Competition is the STRUGGLE FOR RESOURCES WHICH ARE IN SHORT SUPPLYPLANTS compete for Light,Nutrients and WaterANIMALS compete for Food, Territorities,Shelter, and Water

EACH SPECIES AFFECTS THE DISTRIBUTION OF OTHERS..

Where do decomposers come in?

•When living things die their bodies are broken down by decomposers so releasing the elements they contain.

•These minerals can be used by plants to grow so the cycle repeats over again

An example of Fungi You know

The Nitrogen CycleNitrogen in the air

Den

itri

fyin

g

bacte

ria

Eating

Nitrates in the soil

N2 fi

xin

g b

acte

ria wast

e

NH3 and its compounds

Nitrates absorbed by roots

N2 fixing bacteria

Decomposing

FertilisersNitrifyingbacteria

Lightning

Formation of

oxides of

nitrogen

…On pollution

Pollutants may REDUCE the biodiversity in an ecosystemEg fossil fuels produce Sulphur Dioxide when burnedThis can cause ACID RAIN

This can lower the pH in Lochs killing some INVERTEBRATESAnd FISH

Pollution and Biodiversity…

If untreated sewage enters a river or lake it provides food for BACTERIA.Their population numbers increaseThey use up all the oxygen in the waterSpecies which cannot tolerate low Oxygen levels die out

THIS RESULTS IN A DECREASE IN THE VARIETY OF SPECIES

DO dissolved oxygen BOD biochemical oxygen demand

The oxygen decline and rise downstream from a point source is called the oxygen sag.

The Biodiversity crisis

Human activity can cause habitat destruction and pollution.This contributes to the extinction of many species ; a reduction in the overall number.Eg Deforestation, for housing,timber and agriculture

CONSERVATION MEASURES HELP MAINTAIN BIODIVERSITY

WHY IS BIODIVERSITY SO IMPORTANT ?

FOOD….Eg fish from the North Sea

RAW-MATERIALS…such as timber and rubber

MEDICINES…may come from as yet undiscovered plants

RECREATION…appreciation of the variety of species in the countryside.

AND…MAINTAINING GENETIC VARIATION……..

Grazing and Biodiversity…

Grassland is made up of a variety of plantsSome species grow quickly and dominateSome species don’t grow as quickly and struggle to compete and surviveGRAZING is the eating of plants by herbivores

UNSELECTIVE GRAZERS EAT ALL TYPES OF PLANT

Intensity of Grazing…

LOW levels of unselective grazing allows the grasses to grow and out compete other less vigorous species.This REDUCES the variety of speciesMEDIUM levels keep the grasses in check allowing less vigorous species to survive.This INCREASES the variety of speciesHIGH levels result in OVERGRAZING.This DECREASES the variety of species