B4

Define Population, Community, Habitat and Ecosystem

Population- Group of living things of same species in same place

Community- Where populations of all diff. species live and co-exist together

Habitat- Where organisms live

Ecosystem- Same as community but includes habitat and non-living elements of a place

Difference between Biotic and abiotic factors affecting an ecosystem

Biotic factors- Living factors eg. Predator and prey

Abiotic- Non-living factors eg. Light intensity, temp, moisture level, soil pH

Why do we sample?

Find out the presence/distribution of organisms in an area when it’s impossible to count them all

For results to be reliable, they need to be random and repeated so they’re representative

How do we measure distribution using quadrats

Abundance- For larger plants which there’s only a few of and easy to count. Count how many within whole quadrat

Percentage cover- “smaller” plants which there are lots of and hard to count. Count how many squares are at least half-filled in the quadrat and create a fraction

How to calculate Population size

Population size= (no. in 1st sample x no. in 2nd sample)/no. in 2nd sample previously marked

Why does Biomass decrease at each trophic level?

Energy transferred to producers by sunlight. Producers only transfer 1% of this into chemical stores via photosynthesis (rest reflected)
Half of the energy transferred by photosynthesis is transferred in respiration
Remaining energy transferred to increase plant’s biomass

How is biomass transferred in animals?

Loss:
Energy from respiration transferred by heating surroundings
Used to provide energy for movement, growth etc.
Lost in urine and faeces

Gain:
Turned into new biomass as it grows
Biomass intake from eating (only 10% of eaten biomass turns into new biomass)

Difference between egestion and excretion

Egestion is the process of removing undigested food from body in faeces whilst excretion is removing waste products through excretion (eg. sweating)

How to calculate efficiency of biomass transfer

(Biomass available after transfer/Biomass available before transfer) x 100

Difference between abundance and distribution

Abundance- how many there are and distribution is where they are

What do plants compete for and what do animals compete for?

Plants- Light, water, space and minerals

Animals- Food, mates, shelter, territory

What are the different types of competition

Interspecific competition- Competition between members of different species

Intraspecific competition- Competition between members of same species

What is an ecological niche

Ecological niche- Organism’s place in an ecosystem
Includes: Where it lives, what it eats and what it does

The more similar two species’ niches are, the more competition there are between them

Diff. types of predator-prey relationship

As prey increases, predators increase since more food
As predators increase, prey decrease as they get hunted
As prey decrease, predators decrease as not enough food
As predators decrease, prey increases as they get hunted and eaten less so can reproduce more

Cycle repeats

Define parasitism

Parasites are organisms that live in close association with its host. Feeds on host and does it harm.

Host-parasite relationship very specific as parasites tend to be very specialised and can only live on 1 host

As no. of hosts increase, no. of parasites increase and vice versa.

Define mutualism

Where 2 diff. species help each other survive. Called mutualism if they live close together and benefit from relationship

If one increases, so does the other and vice versa

Outline the water cycle

Evaporation and transpiration add water to atmosphere
Sun heats up water speeding these processes up and also providing the energy for them
Water vapour reaches the air which then condenses and forms clouds
This comes back down in the form of precipitation

Outline the carbon cycle

Carbon dioxide leaves the air through photosynthesis in plants and plankton, re-enters through respiration
CO2 transferred to animals through feeding
CO2 enters the atmosphere through respiration
Animal dies, CO2 enters atmosphere through decomposition
If it doesn’t decompose, then it forms fossil fuels over millions of years.
CO2 enters atmosphere through combustion

Outline nirogen cycle

Nitrogen in the Air – 78% of the air is nitrogen, but plants and animals can't use it directly.

Nitrogen Fixation – Special bacteria in the soil or root nodules convert nitrogen gas into nitrates . Lightning can also do this.

Absorption by Plants – Plants absorb nitrates from the soil and use them to make proteins for growth.

Consumption by Animals – Animals eat plants (or other animals), getting nitrogen for their own proteins.

Decomposition – When plants and animals die, decomposers break down proteins into ammonia.

Nitrification – Nitrifying bacteria convert ammonia into nitrates, making it available for plants again.

Denitrification – Denitrifying bacteria convert nitrates back into nitrogen gas, returning it to the atmosphere.

What are Detritivores?

Break down small parts of dead material (detritus- dead plants, animals and waste) which they digest and release as waste
Increases surface area of detritus for decomposers to act on
Includes: Earthworms, maggots etc.

What are Saprophytes?

Most decomposers are saprophytes
Feed by releasing enzymes which digest dead material (extracellular digestion)
Decomposers absorb digested chemicals (Saprotrophic feeding)
Release ammonium compounds into soil
Includes: Bacteria and Fungi

What are the conditions for optimal decay?

Warmth: Microbes able to respire faster so will grow and reproduce faster, increasing ROD

Oxygen: Able to respire faster so grows and reproduce faster, increasing ROD

Moisture: Microbes need water to remain healthy. Chemical reactions need to happen in solution.