1.7 Ecological relationships and energy flow

Ecology

distribution of living organisms and relationships between them

Ecosystem

area where community of organisms live and are affected by range of environmental factors

Biodiversity

measure of the number of species living in an area

Habitat

specific area or environment where a population lives and breeds

Population

number of organisms of single species living in an area

Community

several populations of different species living in habitats close together

Organism

An individual living thing that is part of a much larger ecosystem

Sampling

dividing larger area into small sections as its too difficult to count all organisms

Effective sampling

• reliable, a large sample size is needed – 20 to 30 quadrats counted

• representative of habitat being investigated, placed randomly to produce valid results and avoid bias

Quadrat

small square frame that can be used to count organisms

Belt transect

used to study changes across habitat by using quadrat at regular intervals in straight line

Abiotic factors

non-living factors e.g temperature and light

How do abiotic factors affect distribution

effects survival rates of plants and animals

Wind speed

abiotic factor measured with anemometer which affects rate of water loss by plants, therefore survival rate

Water levels in soil

abiotic factor measured by finding mass of soil sample and heating to constant mass to find moisture

pH levels

abiotic factor measured using pH probe, most plants prefer neutral but some only acidic or alkaline

Light

abiotic factor measured using light meter and all plants need it for photosynthesis

Temperature

abiotic factor measured using thermometer which affects rate of cell reactions (photosynthesis)

Biotic actors

living factors, much harder to measure e.g effect of predators or competitors

Competition between animals

• food

• water

• territory

• mates

Competition between plants

• light

• water

• minerals

• space

Effect of competition

effects population growth with many organisms adapting to individual environments/ competition for resources

Human effect on ecosystem

• deforestation

• pollution

• overfishing

• climate change

How human activities disrupt ecosystems

• alter habitats reducing biodiversity and destabilising food webs which ompact health and endanger species

Grey squirrels

• much larger and was introduced from north america

• now outweighs population of red squirrels

• eats wider range of food and can survive in areas of mixed woodland

• carries disease that is fatal to red squirrels while grey remains unaffected

• struggles to obtain enough food where seeds are small

Heating to constant mass

heating in oven and weighing, repeating this until two readings are the same as water will have been evaporated

Source of energy

the sun, but only about 1% efficiency to plants

Producers

Plants that use light energy to produce sugars and starches through photosynthesis

Animals/ consumers

Feed on plants or other animals to get energy

Herbivores

plant eating animals that are primary consumers

Carnivores

animals who eat other animals that are secondary consumers, but are eaten by tertiary consumers

Food chains

sequence to show flow of energy using arrows between each trophic level

Arrows in food chains/ webs

must be included to show direction of energy flow, consumption and transfer of substances e,g carbon and nitrogen

Food webs

show interconnecting food chains of feeding relationships within a community

How energy is lost from sun to plant

light is reflected off the leaf or passes through the leaf missing chloroplasts

Ways energy is lost between trophic levels

• whole organism not being eaten (skeleton/ fur left behind)

• not all food digested, some passes out in excretion or egestion

• lost as heat in respiration

• energy used for movement, reproduction and growth

Efficiency formula

Output/ input x 100

Short food chains

more efficient as fewer levels for energy to be lost through

Pyramids of numbers

show the number of individual organisms at each trophic level in food chain

Advantages of pyramid of numbers

• simple and easy to construct

• organisms to not need to be killed

Disadvantages of pyramids of numbers

may produce inverted pyramid

does not take into account mass/ size of organisms

Pyramids of biomass

show total mass of living organisms at each trophic level

Advantages of pyramid of biomass

• takes into account size/ mass of organism

• shows flow of energy between trophic levels

Disadvantages of pyramids of biomass

• difficult to collect data

• requires organisms to killed to find dry mass