Studied by 1 personWhat is asexual reproduction?
Reproduction that involves 1 parent and does not involve sex. It produces clones so there is no variation.
What is sexual reproduction?
Reproduction that involves 2 parents and involves sex. It produces offspring that is genetically different to parents so there is variation.
What is variation?
Differences between members of the same species.
What is variation caused by?
Genetic factors - characteristics caused by genes inherited from parental DNA.
Environmental factors - characteristics that change due to the environment.
What are some examples of genetic variation?
Eye colour, blood type etc.
What are some examples of environmental variation?
Tattoos and piercings, competition in plants reducing access to light or water restricting growth etc.
Who worked on the theory of evolution by natural selection?
Charles Darwin and Alfred Russel Wallace.
What does natural selection mean?
Some animals are better adapted to survive than others. Deciding factors include mutation, variation, competition, survival of the fittest and breeding.
What is mutation?
Random changes in genes that cause variation in species.
Why may rates of mutation increase?
Due to ionising radiation.
What is variation? (evol.)
Small differences within a species that makes some individuals better adapted to the environment.
What is competition?
Where organisms compete for survival. Some have toxin-resistant genes.
What is survival of the fittest?
Where those with advantageous genes have a selective advantage over others, enabling them to compete better for resources or survive an antibiotic, pesticide or other toxin that kills others of the species.
What is breeding?
Where organisms that can survive breed, passing on their advantageous genes to the next generation.
What may happen if environmental change is too quick for species to adapt by natural selection?
Extinction may occur.
What is continuous variation?
Variation controlled by more than one gene and environmental factors, e.g. weight and height.
What is discontinuous variation?
Variation controlled by one gene so individuals fit clearly into discrete groups, e.g. eye colour or blood type.
What is cystic fibrosis?
A genetically inherited disease. It causes thick sticky mucus that blocks bronchioles in lungs.
How can cystic fibrosis be treated?
By gene therapy. An inhaler can be used to get the gene into lung cells but as cells renew, the gene is not copied and new cells do not contain the ‘normal’ gene.
How can we model natural selection to show that camouflaged organisms have an advantage against predators?
Arrange small pieces of plain and patterned card on a plain background.
Use forceps to model a predator beak/jaw and record how many of each type you pick up in 15 seconds with the forceps.
This shows that you are more likely to select prey that is more easily seen.
What are some limitations of modelling natural selection?
The model prey does not move and the model background is flat not textured.
What is the human genome project?
A project in which human DNA was studied to find new information and develop ways to treat, cure and prevent disease.
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