How are living things related (evolutionary relationships)?
- Species with similar characteristics often have similar genes as they share a common ancestor, so they’re closely related. They often look very alike and tend to live in similar types of habitat e.g. whales and dolphins
- Occasionally, genetically different species might look alike too. E.g. dolphins and sharks look pretty similar as they’ve both adapted to living in the same habitat. But they’re not closely related- they’ve evolved from different ancestors.
- Evolutionary trees show common ancestors and relationships between organisms. The more recent the common ancestor, the more closely related the two species.
What are interaction of organisms (ecological relationships)?
- If we see organisms in the same environment with similar characteristics (e.g. dolphins and sharks) it suggests they might be in competition (e.g. for the same food source).
- Differences between organisms in the same environment (e.g. dolphins swim in small groups, but herrings swim in giant shoals) can show predator-prey relationships (e.g. dolphins hunt herrings).
How does natural selection explain how evolution occurs?
- Charles Darwin’s theory:
- Individuals within a species show variation because of the difference in their genes.
- E.g. some rabbits have big ears and some have small ones.
- Individuals with characteristics that make them better adapted to the environment have a better chance of survival and so are more likely to breed successfully.
- E.g. big-eared rabbits are more likely to hear a fox sneaking up on them, and so are more likely to live and have millions of babies.
- The genes that are responsible for the useful characteristics are more likely to be passed on to the next generation.
- E.g. all the baby rabbits are born with big ears.
How can evolution occur due to mutation?
- Most of the time mutations have no effect, but occasionally they can be beneficial by producing a characteristic.
- This characteristic may give the organism a better chance of survival.
- The beneficial mutation is more likely to be passed on to future generation by natural selection.
- Over time, the beneficial mutation will accumulate in a population e.g. some species of bacteria have become resistant to antibiotics due to a mutation
Why did people not agree with Darwin?
- It went against common religious beliefs about how life on Earth developed.
- Darwin couldn’t give a good explanation for why these new, useful characteristics appeared or exactly how individual organisms passed on their beneficial characteristics to their offspring.
- There wasn’t enough evidence to convince many scientists, because not many other studies had been done into how organisms change over time.
- Mechanism of inheritance and variation was not known until after 50 years the theory was published.
What was Lamarck’s theory of evolution?
- Lamarck (1744-1829) argued that if a characteristic was used a lot by an organism then it would become more developed during its lifetime.
- E.g. if a rabbit used its legs to run a lot (to escape predators), then its legs would get longer.
- Lamarck believed that these acquired characteristics would be passed on to the next generation.
- E.g. the rabbit’s offspring would have longer legs.
How can scientists develop different hypotheses from similar observations?
- Scientists came up with different hypotheses to explain similar observations.
- Scientists developed different hypotheses because they had different beliefs or they have been influenced by different people.
- E.g. Lamarck and Darwin both had different hypotheses to explain how evolution happens in the end.
What is Darwin’s theory of evolution?
- Natural selection:
- All species of living things have evolved from simple life forms that first developed more than three billion years ago.
Who came up with the idea of natural selection?
•Charles Darwin.
When was genes and mutation discovered?
•They weren’t discovered until 50 years after Darwin’s theory was published.
What is the only way to find out whose hypothesis is right?
•To find evidence to support or disapprove each one.
Why is Lamarck’s theory rejected?
- The experiments didn’t support his hypothesis.
- E.g. if you dye a hamster’s fur bright pink, its offspring will still be born with the normal fur colour the new characteristic won’t have been passed on.
How did the discovery of genetics support Darwin’s idea?
- It provided an explanation of how organisms born with the beneficial characteristics can pass them on (i.e. via their genes).
- There’s so much evidence for Darwin’s idea that it’s now accepted hypothesis (a theory).
What is classification?
•Studying the similarities and differences between organisms allows us to classify living organisms into animals, plants and microorganisms.
What is classification used for?
- It helps us to understand evolutionary and ecological relationships.
- Models allow us to suggest relationships between organisms.
What are evolutionary trees (models).
•They are used to represent the relationships between organisms.
What do evolutionary trees indicate?
- How long ancestors of ape species diverged from each other.
- That humans share a common ancestor with chimpanzees more recently than ape species.
Draw an evolutionary tree to represent the relation between human and ape species.
- Arrow point up showing time.
- Gibbons.
- Orangutans.
- Gorillas.
- Chimpanzees.
- Humans.
What is Darwin’s theory of natural selection?
- Organisms produce large numbers of offspring.
- Individual organisms within a particular species may show a wide range of variation because of differences in their genes.
- There is a struggle for all organisms to exist.
- Individuals with characteristics most suited to the environment are most likely to survive to breed successfully.
- The genes which have enabled these individuals to survive are passed onto the next generation.
- This can result in changes in the characteristics of a species.
How do mutations occur?
- When the DNA is replicated before cell division.
* When chromosomes are separated during cell division.
What do mutations do?
- Genes control the synthesis of proteins.
- Change in a gene or a new sequences of genes can result in other proteins being synthesised.
- This can change a characteristic.
- Most mutations are harmful or fatal.
What are mutations?
•A change in an organism’s DNA.
What are the difference between organisms?
- Plants make their own food (by photosynthesis) and are fixed in the ground.
- Animals move about the place and can’t make their own food.
- Microorganisms are different to plants and animals e.g. bacteria are single-celled.
What are the different stages of an evolutionary tree?
- Distant ancestors.
* Recent ancestor.
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B1.2 Nerves And Hormones109
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B1.5 & 1.6 Energy And Biomass In Food Chains & Waste Materials From Plants And Animals48
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B1.3 The Use And Abuse of Drugs45
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B1.4 Interdependence And Adaptation42
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Exam questions- Diet and Excercise22
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B1.1.1 Diet And Exercise60
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B1.8 Evolution24
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B1.1.2 Infectious Disease80
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B1.7 Genetic Variation And Its Control59
