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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