Unit 2 Evolution Test Beverley Ceja
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7. The green frog (Lithobates clamitans clamitans) is found in many parts of the
United States. The table contains some information about this frog.
It increases opportunities for offspring to compete for
limited resources
It increases the probability that some offspring will survive
long enough to reproduce.
Reproduction Facts for L. clamitans clamitans
Breeding season
Late spring
Length of breeding 1 to 3 months
season
Breeding habitats Swamps, ponds, marshes, slow-moving
streams
Number of eggs per 1,000 to 5,000
clutch
When eggs hatch
3 to 7 days
о
О
It increases the probability that moving water will promote
gene flow from one population to another,
о
О.
It increases the chance of the recombination of alleles,
leading to genetic drift in the population.
Why does the ability to lay 1,000 to 5,000 eggs increase the fitness of the
species L. clamitans clamitans?
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an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.

genetic variations are caused by mutations which are random in the population