B14: Genetics & Evolution

What are the two types of evidence for evolution?

What are the two types of evidence for evolution?

Fossils & antibiotic resistance in bacteria

What is the evidence for Darwin's theory of natural selection?

Characteristics are passed to offspring in genes, in fossil records & 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

What are the 3 ways fossils can be formed?

1. from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent known as preservation

2. when parts of the organism are replaced by minerals as they decay known as gradual replacement of minerals (skeletons made of rock)

3. as preserved traces of organisms (casts & impressions)

What conditions are needed for decay?

Oxygen, moisture, warmth

Give examples of places where preservation could take place:

Glaciers (Too cold for microorganisms that carry out decomposition to survive), peat bogs (too acidic for microorganisms), amber & tar (insufficient oxygen so microorganisms can't respire aerobically)

How are casts formed?

When an organism is buried in soft material such as clay, it hardens when the organism decays which leaves a gap that is the same size and shape as the organism

Give examples of casts:

Animal burrows, plant roots

How are impressions formed?

When animals leave marks on the ground that stay there over time

Give an example of an impression:

Footprints

Why is the fossil record incomplete?

- fossils that formed millions of years ago may have been destroyed by geological activity

- many early organisms were soft bodied, and soft tissue tends to decay away completely so no traces were left behind

- we haven't found all the fossils yet

What do fossils show?

The fossil record provides evidence about the history of life and past environments on Earth. The fossil record also shows how different groups of organisms have changed over time.

When does extinction occur?

When there are no remaining individuals of a species still alive

What factors contribute to the extinction of a species?

Environment changes too quickly (eg. habitat destruction, global warming), introduction of new predators that either kills the whole species or outcompetes it, introduction of new disease, catastrophic event

Why do bacteria evolve rapidly?

They reproduce at a fast rate

What is antibiotic resistance?

Evolution of bacteria to be able to survive exposure to antibiotics

What causes new strains of bacteria?

mutations of bacterial pathogens

How does antibiotic resistance population arise?

some strains are resistant to antibiotics so are not killed so therefore reproduce and as a result the population of resistant strain increases.

Why will the antibiotic resistant spread faster?

people are not immune to it and there is no effective treatment.

Give an example of a bacteria that is antibiotic resistant:

MRSA

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

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

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

3. the agricultural use of antibiotics should be restricted

How do farmers use antibiotics in agriculture?

They give antibiotics in the food given to healthy animals to prevent them from getting ill in the first place and allow them to grow faster

Why is the increase of the antibiotic resistant population a problem?

The development of new antibiotics is slow and costly so won't keep up with the emergence of new strains

why did Carl Linnaeus come up with the Linnaean System?

difficult to name species based on physical characteristics only, there were different names used globally for the same species, simple names don't show how related species are to one another

What did Carl Linnaeus develop?

a system to classify organisms into groups depending on their structure and characteristics

What was the Linnean system?

Kingdom (plant or animal), phylum, class, order, family, genus and species

How are organisms named?

the binomial system of genus and species

How do we write the binomial name of a species?

all lower case except the first letter of the genus & all in italics

Why was the binomial system important?

Each species has an unique name & allows scientists to discuss individual species

Describe the impact of development sin biology on classification systems:

As evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes progressed, new models of classification were proposed

What did Carl Woese do?

Developed the three domain system

What was the classification system order after Woese's three domain system was introduced?

Domain, Kindgom, phylum, class, order, family, genus and species

What are the three domains that were added to the Linnean system above kingdoms?

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

2. Bacteria (true bacteria)

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

What are evolutionary trees used for/

Evolutionary trees are used to show how organisms may be related by linking common ancestors