GCSE OCR GATEWAY BIOLOGY : ORGANISATION IN ECOSYSTEMS COMPLETE REVISION

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GCSE OCR BIOLOGY ORGANISATION IN ECOSYSTEMS COMPLETE REVISION SUMMARY

ORGANISATION IN ECOSYSTEMS

Organisation in ecosystems

Abiotic factors affecting the abundance and distribution of organisms
Biotic factors affecting organisms in ecosystems
Abiotic factors (data)
Biotic factors (data)
Competition in a community
Interdependence within a community
Trophic levels
Pyramids of biomass
Transfer of biomass

Ecosystem –

Groups of communities with its living and non-living factors

Biosphere – Groups of different Ecosystem

Organisms, Populations, and Communities: In a forest, each pine tree is an organism. Together, all the pine trees make up a population. All the plant and animal species in the forest comprise a community.

Ecosystems: This coastal ecosystem in the southeastern United States includes living organisms and the environment in which they live.

The Biosphere: Encompasses all the ecosystems on Earth.

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ECOSYSTEM

It is a segment of nature consisting of a biological community and its physical environment both interacting and exchanging materials as well as energy. e.g – pond ecosystem.

Ecosystem is the group of communities interacting with the biotic and the abiotic factors.

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ABIOTIC FACTORS

Non-living substances and factors of an ecosystem. E.g temperature, light, wind.

Most of the abiotic factors affects photosynthesis which affects the producers which inturn affect the complete food chain.

Light – Less light limits the photosynthesis and affect the entire food chain Plant in low light have broader leaves to increase surface area for absorption.

Water – Water is required for growth. Less water limits the photosynthesis and affect the entire food chain

pH – The low pH makes the soil acidic and limits the growth of plants and affect the entire food chain

Temperature – Temperature also limits the rate of photosynthesis which affects the food chain

Oxygen – The oxygen is required for the growth of the plant. In low levels of oxygen the organisms cannot survive

Carbon Dioxide – Carbon dioxide is required for growth. Less water limits the photosynthesis and affect the entire food chain.

Wind – Plants growing in high wind adapt different shapes. Wind also affects the rate of transpiration.

BIOTIC FACTORS

Constitute all the living members of an ecosystem. E.g Producers, Consumers, Decomposers.

FOOD – Food availability helps the species to grow and reproduce.

PATHOGEN – A pathogen can cause infectious disease d affect the growth of the population and can also wipe the whole population

PARASITES – Parasites can limit the growth of the host and affect the • population of the community.

COMPETITION – Increasing competition can affect the growth of the population and can outcome the individual of a population

PREDATORS – Increase in predation can decrease the population of the prey.

INTERDEPENDENCE

One species is dependent on other. Like plants are dependent on insects for seed dispersal and pollination.
Herbivores are dependent on plants for food.
If one species is removed it affect the other species.

COMPETITION IN PLANTS AND ANIMALS

INTERSPECIFIC COMPETION	INTRASPECIFIFC COMPETION
It is the competition between the members of different species.	It is the competition between the members of the same species.
Food Territory Resources	Food Territory Mating
It leads to the movement of species to a new place, adaptation or extinction

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Organisation in ecosystems

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ADAPTATIONS

Special Features that give the organisms the survival advantage and helps the organism to survive in the extreme conditions.

PLANT REQUIRMENTS

Water, space, minerals, carbon dioxide for photosynthesis
Oxygen for respiration.
Major adaptations they have make them successful in getting these components from the environment

ANIMAL REQUIREMENTS

Food to survive
Oxygen for respiration
Mate to reproduce.

Adaptations can be structural, behavioural and functional adaptations.

PLANT ADAPTIONS

PLANT CHALLENGES	PLANT ADAPTATIONS	EXAMPLE
Water loss and dry conditions in desert	Small leaves; Leaves reduced to spines to decreases the surface area for water less. Extensive root system to absorb maximum water and succulent stems to store water. Plants are also covered with waxy cuticle to limit water loss	Cactus where leaves are reduced to spines Marram grass which has curled leaves and sunken stomata to trap moist air to limit water loss.
Lots of rain and water with less light in rainforest	Leaves are broad to trap maximum sunlight. They have thin cuticle	Epiphytes like Lianas
Plant growing in low nitrogen soils.	The plants trap insect and digest them to fulfil their nitrogen and mineral requirements	Carnivores plant like Venus Flytrap
Plants prone to insect attack	These plants secrete chemicals like alkaloids or tannins to repel insect	Tobacco produced Nicotine.
Aquatic Plants growing in excess water and less light	Flexible stem to withstand water current. Broad leaves to absorb maximum light. They have hair spaces in leaves	Water Lillies

ANIMAL ADAPTATIONS

	DESERT ANIMALS Hot, dry conditions	ARCTIC ANIMALS Extreme cold
Structural	They have large ears to give off maximum heat. They are small with large surface area to volume ratio.	They have small surface area to volume ratio to prevent heat loss. They have fur or thick fat deposit to provide insulation. White fur also comouflage with the ice.
Behavioural	They are more active during early morning and evening. When it is too hot or too cold they rest in burrows.	Polar bears form big dens and are strong swimmers and can swim through ice.
Functional	Produce very concentrated or no urine.	The fur or the coat change colours in summer and winters.

EXTREMOPHILES

EXTREME TEMPERATURE	EXTREME SALT
They have enzymes that work at high temperature and do not get denatured.	They have salt glands to expel excess salt.
For extreme cold they have antifreeze.	They also have adaptations in the cytoplasm so that they cannot gain or loose water.

STUDYING COMMUNITIES

Quadrat Method – Random squares are placed at different point and the species within that squares are counted.

Transect Method – A line is placed and the species that are within this line or few cm above or below this line are counted and recorded.

Sample Size – The sample to be take for observation.

Mean – It is the statistical value calculate by adding all the values divided by total number of values.

Median – It is the middle value of the data.

Mode – The value that has the greatest frequency.

Range: It is the highest value take away the lowest value.

TROPHIC LEVELS

Producers: They produce their own food as they can photosynthesize and converts Sun’s energy to chemical energy.

Primary Consumers – They are herbivores which feeds on plants.

Secondary Consumers – They are carnivores or omnivores which feeds on herbivores.

Tertiary Consumers – They are at the top of food chain

Decomposers – Feed on dead and decay matter.

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FOOD CHAINS

It is the relationship of who eats whom.
At each level there is a loss of energy and only 10% is transferred to the next trophic level so the food chains are mostly restricted to 3-4 tropic levels.
Sun is the principal source of energy driving the whole food chain.

PREDATOR- PREY RELATIONSHIP

Prey increases

Predator increases

Prey Decreases

Predator decreases

PYRAMIDS OF BIOMASS

Graphical representation of the mass of the living organism at each level.
It is upright as :-
Not all the biomass is eaten by the next trophic level
Some of the biomass is lost as energy at each trophic level.
Some of the biomass is lost as waste product at the trophic level.

Biomass is the mass of the materials contained in the living organisms.

PYRAMIDS OF NUMBERS

It is the graphical representation of the number of organisms at each trophic level.
It can be upright, inverted or upside down.

ENERGY TRANSFER PYRAMID

It is the graphical representation of energy at each trophic level.
Energy Lost at Each trophic Levels

a) Energy is required for movement, growth and repair
b) Energy is lost in digestion
c) Energy is lost in maintaining constant body temperature
d) Energy is lost as heat during respiration.

CYCLING OF MATERIALS

Decomposers play an important role in material recycling
Decomposers feeds on dead and decay matter. They break the organic matter into simple components and return them to soil.
The products carbon dioxide into the atmosphere by the process of decomposition.
Bacteria and Fungi

Proteins in the dead and decay matter is converted into nitrates and returned to soil.

Disclaimer:

I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.

References:

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