Week 8 Flashcards
What evidence supports the theory that dinosaurs were the ancestors of birds?
Fossilised feathers were found on a dinosaur called Anchiornis.
What do fossils of fish and amphibians of the Devonian period have in common?
Bones and limbs
Do these bones of fish and amphibians stay the same over time?
No. There is a gradual change in the structure of the whole limb over time.
Define evolution?
A genetic change in the characteristics of a species over many generations, resulting in the formation of a new species.
Define generation?
The time between the birth of an individual and when that individual produces their own offspring.
The fossil of which animal is a good example of changes over generations?
The horse
How many different genera of the horse have been found and dated?
17
Name the four changes in the horse and the height of each one?
Hyracotherium-0.4 m
Mesohippus-0.6 m
Merychippus-1 m
Equus-1.6 m
How are organisms classified?
On the basis of their structure
What did biologists studying evolution from 150 years ago think about structure.
Organisms that were very similar in structure must be related
Describe natural selection?
An environmental factor acts on a population and some organisms have more offspring that others
What is a selective agent?
The environmental factor that acts on a population
Define biotic factor?
A living thing
Eg: predation, bacterial infection, competition
Define physical factor?
A more environmentally based factor
Eg: susceptibility to fire, soil nutrients
Describe how selective agents that kill individuals act?
By preying on the poorly adapted and less fit individuals
Describe how sexual selection works?
Organisms are selected to breed based on what they look like or their sexual appeal
Describe how selective agents change populations?
Favoured individuals pass on their genes and features to the next generations.
Populations change and they become better suited to their environments.
What is meant by variation?
Natural selections in the population caused by differences in genes.
How is natural selection related to genetics?
Natural selection is the change in the proportion of a genotype of a species over many generations due to the environmental selection of a phenotype.
What did Charles Darwin propose?
Natural selection could result in the formation of new species
What does the theory of evolution propose?
Similar species must be closely related to each other
What does similarity between species indicate?
They had a common ancestor at some time in the past.
Which creature did Darwin study to come up with his theory?
Finches
Which part of the creature caused Darwin to believe that finches had a common ancestor?
Their beaks
What did he believe caused what did Darwin believe caused the difference in the finch’s beaks?
The different beaks had been selected for the different food sources found on different islands
Can you determine if two organisms are from the same species from their anatomy?
No, it’s impossible
What is the test for a species?
To see if two organisms could interbreed to produce fertile offspring under natural conditions.
Give an example of an interbred species?
The mule, produced by crossing a horse and a donkey.
Which method is mostly used by biologists today to see if organisms are the same species?
They study DNA and also identify the similarities in the amino acid and arrangement in the proteins they make.
Define specification?
The process by which one species splits into two or more separate species
Define biodiversity?
The number and range of species that exist, either on the whole Earth or any of Earth’s ecosystems
How is specification related to biodiversity?
Specification has resulted in the high level of biodiversity on the Earth
List the three basic steps of specification?
1) Variation
2) Isolation
3) Selection
Which group of organisms were the ancestors of birds?
Dinosaurs (the theropods)
Under what condition is natural selection able to act?
There must be variation in the population or specification cannot occur
Define isolation?
Where different groups of the breeding population are prevented by some mechanism from interbreeding