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Study Guide

BIOL 1001- Final Exam Guide - Comprehensive Notes for the exam ( 33 pages long!)


Department
Biology
Course Code
BIOL 1001
Professor
Tamara Kelly
Study Guide
Final

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York
BIOL 1001
Final EXAM
STUDY GUIDE

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BIOL 1001 STUDY #2
Non-Random Mating:
Gametes from individuals that live close to each other are more likely to combine than gametes from individuals that live
farther apart.
In vertebrates, insects, and other animals, females don’t mate at random, but actively choose certain males
Three mechanism that violate HWE:
Inbreeding:
Mating between relatives
Relatives share a recent common ancestor
Individuals that inbreed are likely to share alleles they inherited from their common ancestor
Inbreeding increases homozygosity inbreeding takes alleles from heterozygotes and puts them into homozygotes
changes genotype frequencies not allele frequencies
Inbreeding depression a decline in average fitness that takes place when homozygosity increases and heterozygosity
decreases in a population. Results from:
o Many recessive alleles represent loss of function mutations inbreeding increases frequency of homozygous
recessive individuals.
loss of function mutations are usually deleterious or even lethal when they are homozygous.
o Many genes especially those involved in fighting disease are under intense selection for heterozygote
advantage.
Homozygous individual for these genes has lower fitness
Heterozygote advantage Sickle Cell Anemia
It does not cause evolution directly because it does not change allele frequencies
o It can speed the rate of evolutionary change
Increases the rate at which purifying selection eliminates recessive deleterious alleles from a population
Assortative Mating:
Takes place when mating is non-random with respect to specific traits
Positive Assortment individuals choose mates that share a particular phenotypic trait with them
Negative Assortment individuals choose mates that differ in a specific phenotypic trait
Does not cause evolutionary change but may change genotype frequencies
Sexual Selection
Occurs when individuals within a population differ in their ability to attract mates
Favors individual with heritable traits that enhance their ability to obtain mates.
o Stronger in males than females (fitness is dependant on how many females they mate with)
Directly has reproductive success
Intersexual Selection Between different sex (female choses the male based on honest signals, fitness trade-offs)
Intrasexual Selection Between the same sex (male-male competition)
Theory: The Fundamental Asymmetry of Sex:
Bateman-Trivers Theory about how sexual selection works:
o Contains two elements: a claim about a pattern in the natural world and a process that causes the pattern
o Pattern sexual selection usually acts on males more strongly than on females.
Traits that attract members of the opposite sex are much more highly elaborated in males
o Explaining the Pattern “eggs are expensive, but sperm are cheap”. Energetic cost of creating a large egg is
enormous whereas a sperm contains few energetic resources
fundamental asymmetry of sex In most species, females invest much more in their offspring than do males
o Has 2 consequences:
o Since eggs are large and energetically expensive, females produce relatively few young over the course of a
lifetime.
Female’s fitness is limited not by the ability to find a mate but primarily by her ability to gain the resources
needed to produce more eggs and healthier young
o Sperm are simple to produce that a male can father almost limitless number of offspring
Male’s fitness is not limited by the ability to acquire the resources needed to produce sperm but by the
number of females he can mate with.
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Predictions of the Bateman-Trivers Theory:
1) If females invest a great deal in each offspring, then they should protect the investment by being choosy about their mates.
Conversely if males invest a little in each offspring, then they should be willing to mate with any female.
2) If there are an equal number of males and females in the population, and if males are trying to mate with any female
possible, then males will compete with each other for mates
Basically there should be 2 types of sexual selection: a female choice and male-male competition
If male fitness is limited by access to mates, then any allele that increases a male’s attractiveness to females or success in
male-male competition should increase rapidly in the population.
o Sexual selection should act more strongly on males than females.
Female Choice for “Good Alleles”
Experiment with bird species found that females prefer to mate with males that are well fed and in good health.
key observations:
1) in many bird species, the existence of colourful feathers or a colourful beak is due to the presence of the red and yellow
pigments called carotenoids
2) Carotenoids protect tissue and stimulate the immune system to fight disease more effectively
3) animals cannot synthesize their own carotenoids, but plants can. To obtain carotenoids, animals have to eat carotenoid
rich plant tissues.
Observation suggest healthiest and best nourished birds in population have the most colourful beaks and feathers.
Sick birds have dull colouration because they are using all of their carotenoids to stimulate their immune system
Female Choice for Parental Care:
In many species, females prefer to mate with males that care for young or that provide the resources requires to produce
eggs.
Females may choose mates on the basis of:
o Physical characteristics that signal male genetic quality OR
o Resources or parental care provided by males OR
o Both.
Male-Male Competition:
Study done on elephant seals, found that:
Males that own beaches with large congregations of females father large numbers of offspring. Males that lose fights father
few or no offspring
The alleles of territory-owning males rapidly increase in frequency in the population
If the ability of win fights and produce offspring is determined primarily by body size, then alleles for large body size have
a fitness advantage, leading to the evolution of large male size. Fitness Advantage is due to sexual selection.
Consequences of Sexual Selection:
Since sexual selection is more intense in males than females, males tend to have more traits that function only in courtship
or male-male competition
o Females survive to adulthood to get a mate, males do not.
Sexual Dimorphism refers to any trait that differs between males and females
o E.g. male lions have a mane, female lions do not.
Sexual selection also violates the Hardy Weinberg Principle causes certain alleles to increase or decrease in frequency
and results in evolution (different from inbreeding and Assortative mating).
ANIMALS USUALLY MAKE DECISIONS IN A WAY THAT MAXIMIZES THEIR FITNESS
Phylogenies and the History of Life
Phylogeny evolutionary history of a group of organisms
Phylogenetic Tree shows the ancestor-descendant relationships among populations or species, and clarifies who is
related to whom.
o A Branch represents a population through time
o Node point at which two branches diverge. Represents the point in time when ancestral species split into two or
more descendants.
o Tip (terminal node) the endpoint of a branch, represents a group (a species or larger taxon) that is living today or
ended in extinction.
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