The Development Of Understanding Of Genetics And Evolution + Classification Of Living Organisms

The theory of evolution by natural selection is now widely accepted. How did knowlegde of genetics later support his idea?

Evidence for Darwin’s theory is now available as it has been shown that characteristics are passed on to offspring in genes. There is further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria.

What are fossils?

The ‘remains’ of organisms from millions of years ago, which are found in rocks.

How might fossils be formed?

• From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent.

• When parts of the organism are replaced by minerals as they decay.

• As preserved traces of organisms, such as footprints, burrows and rootlet traces.

Why can’t scientists be certain about how life began on earth?

Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity.

What can we learn from fossils?

How much or how little different organisms have changed as life developed on Earth.

When does extinction occur?

When there are no remaining individuals of a species still alive.

What factors might contribute to extinction?

• When the environment chnages too quicky (e.g destruction of habitat)

• A new predator kills them all.

• A new disease kills them all.

• They can’t compete with another new species for food.

• A catastrophic event occurs that kills them all.

Why is it that bacteria can evolve quickly?

Because they reproduce at a fast rate.

What do mutations of bacterial pathogens produce?

New strains. Some strains might be resistant to antibiotics, and so are not killed. They survive and reproduce, so the population of the resistant strain rises. The resistant strain will then spread because people are not immune to it and there is no effective treatment.

What is MRSA resistant to?

Antibiotics

How can the rate of development of antibiotic resistant strains be reduces?

• Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections.

• Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains.

• The agricultural use of antibiotics should be restricted.

Why is it unlikely to keep up with the emergence of new resistant strains?

The development of new antibiotics is costly and slow.

Traditionally, how have living things been classified?

Into groups depending on their structure and characteristics in a system developed by Carl Linnaeus.

How did linnaeus classify things?

Kingdom, phylum, class, order, family, genus and species.

What are organisms named by?

By the binomial system of genus and species.

What is the impact of developments in biology on classification systems?

Advances in biological techniques have had a huge impact on the way that scientists classify organisms on Earth. They have helped them find out to what extent organisms are related to one another.

How did evidence of internal structures become more developed?

Due to improvements in microscopes, and the understanding of biochemical processes.

What due to these developments?

New models of classification were proposed.

Due to evidence available from chemical analysis there is now a ‘three-domain system’ developed by Carl Woese. whatare organisms divided into?

• Archaea (primitive bacteria usually living in extreme environments).

• Bacteria (true bacteria).

• Eukaryota (which includes protists, fungi, plants and animals).

What are evolutionary trees?

A method used by scientists to show how they believe organisms are related. They use current classification data for living organisms and fossil data for extinct organisms.