national 5 biology unit 3

species

a group of similar organisms which can produce fertile offspring

biodiversity

variety of species living in a habitat

producer

organisms which produce their own food

consumer

organisms which rely on eating other organisms for food

carnivore

meat eater

herbivore

plant eater

omnivore

plant and animal eater

prey

an organism which is hunted

predator

an organism which hunts for food

food chain

feeding relationships between a producer and a top consumer

food web

a network of interconnected food chains in a habitat

ecosystem

all the organisms living in a habitat and the non living components which the organisms interact with

niche

the role that an organism plays in a community

a niche describes

- the resources the organism uses in an ecosystem
- the interactions an organism has in the community competition
- the conditions it can tolerate (temperature)

competition in ecosystems occur when

resources are in short supply

interspecific competition

when individuals of different species compete for one or a few of the resources they require

intraspecific competition

when individuals of the same species compete for all resources they require

biotic factors

competition for resources, disease, food availability, grazing, and predation

abiotic factors

non living - temperature, pH, light intensity, and moisture

photosynthesis equation

carbon dioxide + water -chlorophyll-> glucose + oxygen

stages of phtosynthesis

light reactions and carbon fixation

light reactions

- light energy from the sun is trapped by the chlorophyll in the chloroplasts and is converted into chemical energy which makes ATP
- water is split into hydrogen + oxygen, excess oxygen diffuses out of the leaf

carbon fixation

- series of enzyme controlled reaction using hydrogen
- carbon dioxide combines with hydrogen to form glucose
- ATP provides energy for this from light reactions
- glucose can be used for respiration

limiting factors of photosynthesis

temperature, light intensity, carbon dioxide

x% amount of energy is transferred between levels in food chains

10

a small quantity of energy is

used for growth

pyramids of energy show

energy produced at each trophic level

reason for pyramid shape

lots of energy produced by producers over a period of time

pyramids of numbers show

total amount of organisms present in a food chain

reason for irregularities in shape

very large oak tree and smaller herbivores

increasing human population requires

increased food yield

fertilisers provides nitrates to soil to

increase crop yields

nitrates in food production

- nitrates dissolved in soil water are absorbed into plants
- nitrates produce amino acids which are synthesised into plant proteins
animals consume plants or other animals to get amino acids for protein synthesis
- fertilisers can be added to soil to increase the nitrate content of the soil

consequences of the use of fertilisers

- fertilisers leach into freshwater adding unwanted nitrates
- increased algae populations causing algae blooms which kill aquatic plants
- dead plants and algae become food for bacteria
- bacteria use up lots of oxygen, reducing availability for other organisms

what reduces use for fertilisers

GM crops

pesticides can be used to kill off

plants and animals reducing crop yields

as pesticides are passed along food chains

toxicity increases and can become lethal

alternatives to the use of pesticides

GM crops and biological control

mutation is

a random change to genetic material

neutral mutations are

neither beneficial or harmful to organisms

advantageous mutations improve

chance of survival

disadvantageous mutations decrease

selective advantage

mutations are

spontaneous and the only source of new alleles

what increases rate of mutation

radiation and some chemicals

new alleles produced by mutation results in

plants and animals becoming better adapted to their environment

how does a population evolve over time in response to changing enviornmental conditions

variation within a population

species produce more?

offspring than the environment can sustain

natural selection of the fittest occurs when

there are selection pressures

only best adapted individuals

survive to reproduce to pass on favourable alleles to pass on the selective advantage. these alleles increase in frequency within the population

speciation occurs after

a population becomes isolation by an isolation barrier

types of isolation barriers

geographical, ecological, or behavioural

natural selection selects

for different mutations in each group due to different selection pressures

each sub population evolves until

their genetic differences make them two different species