Revision B1a - Environment
Transcript Revision B1a - Environment
Pyramids of biomass show WEIGHT.
Biomass is how much things weigh all together.
Don’t forget the units! E.g.kg.
Darwin the dude said…
1) All species produce more offspring that can survive
2) But population sizes remain pretty constant over time
3) Organisms in a species show wide variation in characteristics
4) Some variation is inherited – passed on to offspring
*In every species organisms have a struggle for survival.
*Those who do survive pass on their great characteristics to
Survival of the fittest!!
Darwin’s views were not popular at first! Especially by the Church
Because Darwin said there was evidence that we were not
‘created’ but instead evolved over time.
Energy from the sun is the source for almost all life on Earth.
Energy is lost at each stage of a food chain.
We can produce more food for humans by…
*growing crops rather than grazing cattle because we reduce
the number of stages in the food chain.
Human activity can affect the environment:
Burning fossil fuels, releasing CFC’s, deforestation, pollution.
Before the exam THINK about what effect each of these have!
Organisms with the greatest change of survival go on to
selecting the characteristics you want in a population
Transfer the characteristic you want into another organism
Fossils provide evidence for evolution.
Fossils can be formed by…
*Gradual replacement by minerals
*Casts and impressions
*Preservation in places where no decay happens
B1a. Topic 1
Organisms compete for resources.
Competition within the same species = intra-specific.
Competition between different species = intra-specific.
Population sizes can be affected by:
Food availability, predators and diseases.
We can use computer models to predict population sizes.
Pros: it can be done from a lab, not a cold field! It is quick.
Cons: Real ecosystems are very complicated, computer models
are only as good as the data that’s been put in it!
Environmental change can cause extinction. Think dinosaurs!
*The environment can change too quickly for species to adapt
*A new predator or disease can kill species
*Species can’t compete with a new species for resources