B3 - Revision Summary

Seite 1

A species is a group of organisms that can breed together to produce fertile offspring.

Cactus- rounded shape,giving small surface area compared to volume to reduce water loss, thick waxy layer to reduce water loss. Fish- gills that extract oxygen from water for respiration, streamlined bodies so they can move through water with as little resistance as possible.

Mutations in the sex cells have greater effect because the mutation will then be passed on to all the cells offspring, causing them to develop new characteristics that might be harmful or useful for survival.

True- the survival advantage will be passed on through natural selection.

Selective breeding involves humans choosing a feature they want to appear in the next generation and only breeding from animals and plants that have it. Unlike natural selection which only selects features that help survival.

Scientists estimate that life on Earth began about 3500 million years go.

Isolation occurs so the organisms can't interbreed, different mutations cause new features, natural selection occurs as well as environmental changes which the organisms adapt to.

Fossils show evidence for evolution as it shows species getting more and more complex as time goes on.

Scientists can use the similarities and differences in DNA to work out how life evolved.

Lamarck's theory was rejected as people concluded that acquired characteristics don't have a genetic basis so they're unable to be passed on to the next generation

Biodiversity is the variety of life on Earth.

One likely cause for the increasing rate of species extinction is humans destroying the habitats of animals.

Scientists classify organisms according to similarities and differences because it makes them easier to study.

When classifying organisms scientists use genetic characteristics.

The classification system shows us the evolutionary relationship between organisms as they will share many genetic and structural characteristics so its likely they evolved from the same ancestor organisms.

Four factors that are essential for plants to live are food,light,co2 & o2 and water.

Organisms have to compete for resources in their environment if there aren't enough to share as some will not survive.

False- organisms depend on each other.

3 main reasons for species becoming extinct are environmental conditions change and species can't adapt. New species is introduced which is a competitor,disease organism or predator. An organism in its food web that is is reliant on becomes extinct.

Energy from the sun is the source of energy for nearly all life on Earth.

Energy is transferred between plants and animals in an ecosystem when animals eat plants and other animals.

Energy is lost at each stage in the food chain through respiration, heat and waste products.

It is unusual to find a food chain with more than five stage because so much energy is lost at each stage that there isn't enough left to support more organisms after 4/5 stages.

In the carbon cycle co2 is turned into carbon compounds through photosynthesis as plants convert the carbon from co2 in the air into sugars.

Carbon is passed between animals in the carbon cycle through eating.

Carbon returns to the air through the combustion of fossil fuels, plant & animal respiration and co2 released from decomposition.

Decomposers break down proteins in dead plants & animals and urea in excreted animal waste into ammonia.

Ammonia is turned into nitrates by nitrifying bacteria that are found in soil.

Nitrogen fixing bacteria turn atmospheric n2 into nitrogen compounds that plants can use.

Denitrifying bacteria turn nitrates back into n2 gas, this is of no benefit to living organisms.

3 non-living indicators that can be used to measure environmental change are temperature, nitrate levels & co2 levels.

Mayfly Nymphs can be used to measure environmental change as they are sensitive to high levels of o2 in water, if lots in the river indicates that water is clean.

Two other living indicators are lichen and phytoplankton.

Sustainability is meeting the needs of today's population without harming the environment so that future generations can still meet their own needs.

Monoculture is when farmers only grow fields containing one type of crop and this is not sustainable because it doesn't help to maintain biodiversity. A single type of crop supports fewer species than a field containing lots of different crops.

Packaging can be made more sustainable by using renewable materials such a recyclable materials or make the materials biodegradable.

Decreasing amount of packaging is more sustainable because even if biodegradable materials are used, they still take a while to break down in landfill sites as there isn't much o2 available. Also, making and transporting any packaging material uses up energy.