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 (zonation) 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 impact 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 on earth, but only about 1% efficiency to plants

Producers

Plants that use light energy to produce sugars and starches through photosynthesis, making it available to other organisms

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 trophic levels for energy to be lost through so more is available to final consumer

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/ collect data

• organisms do not need to be killed

Disadvantages of pyramids of numbers

• may produce inverted pyramid

• does not take into account size of organisms

Pyramids of biomass

show total mass of living organisms at each trophic level

Advantages of pyramid of biomass

• more accurate as takes into account size of organism

• shows flow of energy between trophic levels

Disadvantages of pyramids of biomass

• very difficult to collect data

• requires organisms to killed to find dry mass

Decoposition

process where bacteria and saprophytic fungi break down dead organisms into simple compounds

Saprophytic

obtain nutrients from dead/ decaying organic matter

Steps of decompoition

1. bacteria/ fungi secrete enzymes out onto dead organisms.

2. enzymes digest organic matter outside cells (extracellular digestion)

3. products of digestion are absorbed by bacteria and fungi

Purpose of decomposition

returns nutrients like carbon and nitrogen to abiotic components, so plants use them, supporting biotic components

Remaining materials of decomposition

form humus which improves soil fertility by retaining water and nutrients

Optimum decomposition

• temperature is warm

• water is present

• oxygen is available

Nutrient cycles

plants absorb inorganic nutrients like carbon dioxide and nitrates to build complex molecules which pass through food chains and return to atmosphere/ soil for reuse

Carbon cycle

exchange of carbon between living organisms (biotic) and their atmosphere (abiotic)

How carbon cycle works

carbon is constantly removed from, and returned to, the environment keeping it in balance

Processes involved in carbon cycle

• photosynthesis

• feeding

• respiration

• fossilisation

• combustion

• excretion

• egestion

• decomposition

Photosynthesis in carbon cycle

plants absorb carbon dioxide from atmosphere, only process reducing carbon dioxide levels in air

Feeding in carbon cycle

carbon in biological molecules move through food chain as animals eat plants and other animals

Respiration in carbon cycle

all living organisms release carbon dioxide when they respire, form of excretion

Fossilisation in carbon cycle

if conditions are not favourable for decomposition, dead organisms decay slowly or not at all, they build up if compressed over millions of years can form fossil fuels

Combustion in carbon cycle

burning fossil fuels releases stored carbon as carbon dioxide

Excretion in carbon cycle

waste materials are released by organisms and broken down by decomposers

Egestion in carbon cycle

animals remove undigested food as faeces, which are broken down by decomposers

Global warming

• increasing carbon dioxide levels and other greenhouse gases form blanket around atmosphere

• allows heat from Sun to enter but then traps it, causing temperatures to increase

Burning more fossil fuels

releases carbon dioxide into atmosphere as product

Deforestation

reduces carbon dioxide absorption due to less photosynthesis

Effects of global warming

• melting polar ice caps

• rising sea levels

• flooding

• climate change, storms and drought

• loss of habitat

How rising temperatures effects distribution of organisms

• some species, like polar bears, lose habitats as ice melts

• others migrate to cooler areas, changing local ecosystems

How extreme weather effects distribution of organisms

• frequent storms or droughts make areas unsuitable for organisms

• species move to regions with more stable conditions

How loss of habitat effects distribution of organisms

• rising sea levels and flooding destroy habitats, forcing species to relocate

• deforestation removes shelter and food, displacing organisms

How to reduce effects of global warming

• renewable energy sources like wind and solar

• public transport, cycle, or drive electric vehicles

• energy-saving appliances and insulate buildings

• plant trees to absorb carbon dioxide

Reforestation

planting trees restores habitats, supports wildlife and increases biodiversity

Sustainable wildlands

• only few trees are cut at a time, protecting ecosystems

• replacing trees and areas are left 35-30 years before harvested again, ensuring sustainability

International treaties

• Kyoto (1997) and Paris (2015) set legally binding strategies to reduce CO₂ levels

• 195 countries committed, promoting positive global change

Nitrogen

78% of earths atmosphere, essential to amino acids and proteins, but plants can only absorb it as nitrates

Root hair cells

adapted with long extension to increase surface area for absorption of water and minerals through active transport

Active transport/ uptake

uses energy to transport against concentration gradient, low concentration in soil to high concentration in cell

Conditions for active transport

requires energy from aerobic respiration, presence of oxygen

Minerals absorbed by root hair cells

• nitrates for making amino acids and proteins

• calcium for strengthening cell walls

• magnesium for chlorophyll production

Nitrogen cycle

• Nitrogen fixation

• Feeding

• Decomposition

• Nitrification

• Denitrification

Nitrogen fixation

nitrogen fixing (aerobic) bacteria convert gas into nitrates

Feeding

animals feed on proteins which travel along food chain

Where are nitrogen fixing bacteria found

‘free’ in soil or nodules of legumes

Legumes

plants like peas, beans and lentils

Decomposition in nitrogen cycle

bacteria/ fungi break down protein from dead plants, animals, urine and faeces into ammonia

Nitrification

nitrifying bacteria (aerobic) convert ammonia into nitrates

Denitrification

denitrifying bacteria (anaerobic) converts nitrates into nitrogen gas

Why denitrification is bad

reduces soil fertility/ plant growth, reduced by ploughing soil and improving drainage

Where are denitrifying bacteria found

thrive in waterlogged soil as do not need oxygen

What are fertilisers used for

replace nutrients lost when crops are harvested, containing nitrates to help crops grow

Examples of fertilisers

farmyard manure, slurry, compost or artificial fertilisers like NPK

Advantages of natural fertilisers

• improves soil quality at no extra cost

• nutrients released slowly

• less likely to leach into waterways

Disadvantages of natural fertilisers

• difficult to store and spread

• composition of minerals can vary

Advantages of artificial fertilisers

• easily applied to fields

• easy to monitor level of minerals added (more accurate)

Disavantages of artificial fertilisers

• expensive

• soluble and can leach easily

If nutrients are not replaced

soil eventually loses ability to grow crops

Eutrophication

caused when sewage or fertilisers get leached into rivers and lakes

Leaching

water/ rain washes off substances and carries them away

Eutrophication process

1. Increase nitrate levels

2. Plants die

3. Decomposition

4. Oxygen Depletion

Increased nitrate levels in eutrophication

sewage disposal and fertiliser run-off increase nitrates levels and cause increased growth of aquatic plants and algae (algal bloom)

Plants dying in eutrophication

algae/ plants become overcrowded, shading each other and blocking light for photosynthesis, causing them to die

Decomposition in eutrophication

aerobic bacteria break down dead plants and algae