Topic 4 - Natural Selection and Modification Flashcards
4.1B - How did Darwin and Wallace come up with the idea of natural selection?
In the 19th century it was believed that God made humans and they can’t evolve.
Darwin visited the Galapagos Islands in 1835, where he noticed differences between mockingbirds on different islands.
He wondered if the mockingbirds could change if moved to a different area, so he brought these different species to London.
In 1838, Malthus wrote an essay arguing if a person had too many children, some would die due to food scarcity.
Darwin used this theory and applied it to animals, he thought that organisms produced more offsprings normally, so only those best suited to the surrounding live and their characteristics are passed on.
Wallace who also read Malthus’ essay came to this conclusion, so him and Darwin wrote a scientific paper on it.
Later, Darwin published his book ‘The Origin of Species’ and due to this he is well known, however he couldn’t proved variation due to lack of fossil samples.
4.1B - What was the impact of the idea of evolution of modern biology?
Biologists started to think about why organisms changed and how inherited variation happened.
This led to the development of molecular biology and genetics.
4.2 - What is natural selection and genetic variation?
Genetic variation is when the characteristics of individuals change due to differences in genes.
Natural selection ( survival of the fittest ) is when genetic variations of some individuals make them better at coping with change and so are more likely to survive.
4.2 - How does natural selection lead to evolution?
Genetic variation in organisms can happen.
When there is an environmental change, there is more competition.
This leads to natural selection where the variations of the species which are better at coping are more likely to survive.
Natural selection leads to the survivors breeding and passing their variations to their offspring, making the next generation better adapted species.
If the environmental conditions remain unchanged, natural selections happens again and again and a new species evolves, as all the individuals of the species are better adapted.
4.2 - What is an example of evolution?
Woolly mammoths have an ancestor that lived in an area that environmentally changed and got colder.
Due to genetic variation, some animals had hairier skin, which were more likely to survive the cold and food scarcity than less hairier organisms.
More of these mammoths survived and bred, which over time made more hairy mammoths, evolving and forming a new species.
4.3 - How is Darwin’s theory supported by evidence?
In the 1940s, a substance called warfarin was used to poison rats.
When first used, most rats died but within 10 years most rats were resistant to warfarin.
Due to genetic variation, there were some rats that were resistant.
The poison killed non-resistant rats leaving resistant rats to breed.
This also happened in antibiotics ( drugs that kill bacteria ) .
In a population of bacteria, some are more resistant than others and are harder to kill.
People who take antibiotics to treat an infection, stop taking it early as they feel better.
This leaves resistant bacteria still alive, which reproduce and spread, causing infections that can’t be treated with antibiotics as all the bacteria is resistant.
The bacteria was easier to kill at first as the antibiotics were new.
4.4 - What is evolution?
Evolution is a gradual change in the characteristics of a species over time.
4.4 - How do scientists use fossils to prove evolution?
Scientists use fossils and find how old they are and put them in order, but sometimes don’t show smooth changes as some fossils aren’t found yet.
4.4 - How do fossils provide evidence for evolution?
In 1992, scientists discovered 4.4 million year fossils of a female from a human-like species. As more species were found it was nicknamed Ardi.
Ardi was 1.2 m and 50kg, she may have been able to walk upright and her long limbs would have helped her climb trees.
Another species, nicknamed Lucy, lived 3.2 million years ago and was 1.07m.
They could walk upright and their toe bones were arranged like human toes.
In 1960, Leakey found a human species which is more recent, called Homo habilis. They were 1.4-2.4 million years old and were short with long arms but walked upright.
In late 1990s, Homo erectus was discovered in Asia, so most scientists believed that life evolved in Asia.
However a 1.6 million year old skeleton found by Leakey in Kenya proved humans evolved there, which had was tall and strongly built.
4.5 - How do stone tools provide evidence for evolution?
Evidence of ancestors of humans using stone tools dates back to 3.3 million years.
The age of the rocks can be found by working out the ages of different layers of rock. The stone tool is the same age as the layer of the rock.
Older stone tools are very simple and may have been used to kill animals.
More recent tools found are more sophisticated and may have been used to cut and skin meat.
4.6B - How does the anatomy of the pentadactyl limb provide evidence for evolution?
Darwin considers how vertebrates have limbs with five fingers ( pentadactyl limb ). As different animals like birds and dolphins should have limbs designed for different purposes.
As the limb is similar, it suggests that evolution happened from a common ancestor and the bones were not designed for specific purposes.
4.6B - How does the anatomy of the pentadactyl limb provide evidence for evolution?
Darwin considers how vertebrates have limbs with five fingers ( pentadactyl limb ). As different animals like birds and dolphins should have limbs designed for different purposes.
As the limb is similar, it suggests that evolution happened from a common ancestor and the bones were not designed for specific purposes.
4.7 - How are organisms classified as five kingdoms?
In 1735, Linnaeus published his classification system, where organisms were divided into groups based on how it looks.
The largest groups, kingdoms, were plants and animals.
Organisms were then sorted into more smaller groups, the last group contained one type of organisms/species.
Linnaeus used the last two groups ( genus and species ) to name the organism with a binomial name.
Using characteristics for evolution has caused problems for organisms that have similar characteristics but not closely related.
But after accepting the idea of evolution, scientists now have altered the classification system so groups had organisms from common ancestors.
Since Linnaeus’ time, technology has developed and organisms can be studied more closely, helping classification to improve.
Now, cells are studied to sort organisms into the five kingdoms.
4.7 - How has genetic analysis changed the understanding of evolution?
In 1970, scientists found new single-celled organisms with no nuclei, so they were classified under the Prokaryote kingdom as Archaea.
However, genetic analysis showed that all organisms apart from prokaryotes had unused sections of DNA ( sections that don’t code for proteins ).
Archaea had unused sections of DNA, leading Woese to propose that organisms should be divided into three domains:
Archaea - no nucleus and unused sections of DNA
Bacteria - no nucleus and no unused sections of DNA
Eukarya - nucleus and unused sections of DNA
DNA changes slowly over time so the more DNA two organisms have in common, the more closely related they are as they evolved recently.
As genetic analysis get faster, classification is updated as new discoveries are made.
