Variation & Selection Flashcards
What does variation mean?
variation refers to the differences between each organism in a species. Variation is beneficial to a species as it allows natural selection to occur and reduces the risk of extinction from disease. There are two types of variation. Genetic and pheonotypic variation
Define “Genetic Variation”
each organism in a species has a different set of DNA, which is due to genetic variation. Genetic variation is increased during meiosis, which produces allels, which means that when the two gamets fuse an entirely new set of genes are produced
Define “Pheontypic Variation” and give an example
the pheontype of an organism refers to its observable characteristics, such as height or color of the hair. Pheontypic variation can be caused by both genetic variation and environmental factors. Fr example, the potential height of an organism is decided in genes which come from the parents, although some organisms will never reach this height as they do not receive enough nutritions from their environment
explain continuous and discontinuous variation with an example
Variation can be either continuous or discontinuous. Continuous variation results in a range of phenotypes between two extremes, for example, height and weight. Discontinuous variation, however is limited to a discrete number of categories, such as blood group, which is only limited to A, B, AB, O in humans. Discontinuous variation is mainly caused by genes alone.
What is mutation and how does it occur?
Mutation are genetic changes which result in a change in a sequence of DNA bases. These changes can occur due to a variety of factors, including exposure to some chemicals and ionzing radiation.
How are new alleles formed?
when a mutation occurs at a specific allele, this allele may be altered, changing how it functions, this is how new alleles are formed.
what is meant by adaptation?
adaptive features are inherited functional features that help the organism by increasing its fitness, which is the ability of the organism to survive and reproduce in its environment.
How do xerophyte plants adapt to their environmen, explain all the features of a xerophytet?
Xerophytes are plants that are adapted to live in very dry climates such as the cacti. They have a number of adaptive features that help it survive water loss by having
1. fewer stomata: this allows bubbles of moist air to be trapped around them which lowers the water potential gradient so less water is lost from the leaves.
2. small rolled leaves: this reduces the surface area of the leaf and traps moisture to lower the water potential gradient, reducing water loss
3. deep roots: allow the plant to absorb water from the soil, roots are adapted to absorb lots of water when it rains.
4. thick waxy cuticle: this provides a waterproof barrier around the leaf to prevent water loss
