Variation and Natural Selection Flashcards
Continuous variation definition -
In continuous variation there is a gradual change in a characteristic across a population
Three examples of continuous variation
- height
- Weight
- Hand span
Discontinuous variation
In discontinuous variation the population can be clearly divided into discrete groups or categories
Three examples of discontinuous variation
- Ability to roll tongue
- hand dominance
- Blood group
How is genetics a cause or variation (3)
- This can be the result of mutations (random changes to the no, of chromosomes of our genes)
- Meiosis where chromosomes are arranged randomly into each of the gametes formed (all gametes are genetically different)
- The process of fertilisation and reproduction produces different phenotypes (when any two gametes fuse, the genes in that zygote will be different from the genes in any other zygote)
How is environment a cause of variation
- Your experiences through life can affect how you look and behave
- Diet can impact your height and weight
- Your climate can affect your appearance as well (More exposure to sunlight, more melanin produced)
Explain Darwin’s theory of evolution ; (5)
- All living things are at risk to selection pressures (disease, starvation and predators).
- All organisms vary from one another due to variation arising from genes. Some organisms are better adapted to their environment. They are more likely to survive and pass on their useful genetic characteristics
- The weaker, less fit organisms will not survive to breed - their less useful genes will not be passed on to the next generation.
- The survivors are different from their ancestors because only they have successful genes. The slight change between the ancestors and the new generation is called evolution
- If an organism is unable to adapt to the changing conditions in which it lives it will struggle to survive and may become extinct
How do fossils provide evidence for evolution? (3)
- fossils are the remains of living organisms that have been preserved for millions of years
- Fossils not only show what a particular animal or plant looked like millions of years ago but also show how the organism changed over a long period of time
- As it it possible to date rocks to when they were formed (and when an organism was fossilised) it is possible to accurately date the age of the fossil
How do bacteria become resistant to antibiotics? (4)
- When bacteria are treated with antibiotics most are killed
- Some may survive due to a mutation, giving them resistance to the antibiotic
- As The antibiotic has killed the other bacteria in the original population, the resistant bacteria can now reproduce at a rapid rate as there is limited competition for resources
- As they reproduce they pass the mutation on to the offspring - ultimately creating a large population of resistant bacteria
What are living fossils ?
A species that has remained unchanged over long periods of time due to being very well adapted to their environment and their environment is stable
Give an example of a living fossil
Coelacanth
If an organism becomes extinct it is due to it having not been able to evolve to a rapidly changing environment. This could be a result of : (5)
- Climate change
- Hunting
- Introduction of non- native Predators
- spread of disease
- loss of habitat due to human activity
What is artificial selection / selective breeding in food plants and domesticated animals ?(2)
- A process in which humans select individual plants or animals for their desirable genetic characteristics
- e.g appearance, increased food quantity or disease resistance and breed them to produce offspring
Problems with selective breeding : (3)
- Selected animals and plants are similar. All of them have the same features and therefore genes
- Many breeds will die out if they are unable to mate.
- This leads to a loss of genes that may be needed in the future
What variation are histograms used to show?
Continuous variation
