Pyramid Of Numbers

GRASS

RABBIT

FOX

Number decreases

Size increases

The Pyramid of BiomassA pyramid of biomass shows the total biomass at each stage of a food chain.

Biomass is the mass of all the organisms in that population.

Biomass goes down as you move along a food chain, so this gives a pyramid shape.

HOMEWORKSet Tues 28 August Due Fri 31 Aug

Biosphere Booklet

Questions 1 - 17

Population

The number of organisms of the same species present in an

ecosystem

What does the growth rate of a population depend on ?

• Birth rate is measured by counting the number of live births in a population during an interval of time

• Death rate is measured by the counting the number of deaths in a population during an interval of time

• The growth rate of a population depends on the birth and death rates.

Population Growth

Left unchecked a population will grow Exponentially!

This is called a ……

Population Explosion

Human Population Growth

The Human Race is undergoing a Population Explosion.

The growth curve of a population in ideal conditions continues to rise indefinitely because the birth rate is high and the death rate is low.

Factors Limiting Population Growth

Limiting Factors

Disease/Parasites

Predators

Starvation Abundance of Food

Predation Lack of Space

Natural Disasters

Competition

Plants compete for …•Light •Water •Nutrients

Animals compete for …•Food •Water •Shelter •Nesting Sites•Mates

Transparent Lid

Damp Cotton Wool

Radish Seeds Only

Cress Seeds Only

Radish and Cress Seeds

After 5 Days at 240C

Healthy Radish

Healthy Cress

Healthy Radish Sickly

Cress

If the competing individuals are of the same species their needs will be almost identical so the competition will be even more intense !

This results in the stronger more successful competitors surviving and the weaker competitors dying off.

The Nitrogen Cycle !

Nitrogen Gas

Nitrogen in Soil Nitrates

Nitrogen in Plants

Nitrogen in Animals

Death and Decay

Nitrogen in Ammonium Compounds

Nitrogen in Nitrites in Soil

Denitrification by Bacteria

Lightening!

NItRATES

Lightening

Fertiliser

Nitrogen Fixing Bacteria

Leaching

Cropping

Denitrifying Bacteria

Keeping It Balanced!

• Nitrogen Cycle QuestionsNitrogen Cycle Questions1.How much nitrogen gas is there in the air? (1)

2.How can nitrogen be removed from the air? (3)

3.How can nitrogen be added to the air? (1)

4.How can nitrogen be added to the soil? (4)

5.What happens to the nitrogen in the soil? (2)

6.What happens to the nitrogen in plant proteins? (2)

7.How does decay of organisms and their wastes add nitrogen to the soil? (3)

• ANSWER IN FULL SENTENCES