Chapter 18: Variation and selection Flashcards
Define genotypic variation:
variation in genes that all depends on the alleles present
Define phenotypic variation:
variation in appearance that all depends on genes and the environment
Define variation:
Differences between individuals of the same species.
Define continuous variation:
results in a range between two extremes for example height.
Define discontinuous variation:
results in a limited number of distinct phenotypes with no intermediates for example being able to role your tongue.
What is a gene mutation?
is a change in the base sequence of DNA where new alleles are formed.
What increases the rate of mutation?
ionizing radiation and some chemical compounds
What is sickle-cell anaemia?
It’s a mutation that changes the molecule haemoglobin, causing red blood cells to become stiff and sickle-shaped which causes them to get stuck in vessels therefore blocking blood flow.
Define adaptive feature:
an inherited feature that helps an organism increase its fitness.
Define fitness:
The probability of an organism surviving and reproducing in their environment.
What is a xerophyte?
Plants that live in areas with low water availability.
What are some adaptations of xerophytes?
- smaller leaves
- thick waxy cuticle on leave
- totally drop leaves
- store water in succulent stem
- rolled leaves to trap moisture
- microscopic hairs in stomata
What is a hydrophyte?
Plants that live entirely in water.
What are some adaptations of hydrophytes?
- air spaces in roots
- large air spaces in leaves so they can float to water surface
- stomata found on upper surface of leaves
What is natural selection?
The adaptation to a changing environment that maintains variability in an environment and then offspring that are produced contain those alleles that are better suited to their environment. This happens over many generations.
