Study sets, textbooks, questions
Upgrade to remove ads
Terms in this set (52)
States that when certain key conditions are met, a population is in equilibrium for a given genetic trait. If the population is in equilibrium, then there is a fixed mathematical relationship between allele frequencies:
F(AA) = p^2
F(Aa) = 2pq
F(aa) = q^2
Equilibrium only occurs if all five of the following conditions are met:
1. Random Mating
2. No Natural Selection
3. No Genetic Drift
4. No Gene Flow
5. No New Mutations
Individuals do not choose a mate based on their characteristics, but mate at random.
No Natural Selection
All individuals contribute similarly their gametes to the gene pool of the next generation.
No Genetic Drift
Allele frequencies don't change due to random events, or to sampling of too small of a population.
No Gene Flow
Alleles are not added to or lost from the population due to individuals moving (immigration/emigration).
No New Mutations
No New Alleles are introduced in the gene pool.
Natural Selection is
A heritable trait that helps the survival and reproduction of an organism in its present environment.
-By and large, organisms seem to be adapted to their environment.
-However, environments change, and adaptation can become maladaptation quickly... and people make skull mountains out of you.
Plato (Died 348 BC)
Thought that species were static, unchanging entities that were created by the gods.
Aristotle (Plato's Student, died 322 BC)
Introduced the notion of the "scale of nature".
Jean-Baptist's Lamarck (1744 - 1829)
Believed that species came into being from earlier ones through the inheritance of acquired characteristics.
Charles Darwin and Alfred Russel
Figured out why adaptation occurs. Both were inspired by observations of similar species living on different islands, but which had slightly different traits. Adaptation occurs in change through time along with common ancestry.
Charles Darwin On the Origin of Species
Organisms better adapted to their environment would benefit from higher rates of survival than those less well equipped to do. Only the fittest will survive.
The point where Human Population and Food production cross. Occurs when the means of sustenance are not enough to support the population, resulting in population reduction through actual or predicted famine.
Struggle for Existence
The competition that arises when more people are born than can be supported by available resources. Only the fittest make it.
The average contribution to the gene pool of the next generation that is made by individuals of the specified genotype or phenotype.
Darwin and Wallace: 4 Postulates of Natural Selection
1. Variation exists among individuals in a population.
2. At least some of this variation is heritable.
3. Survival and Reproductive success vary among individuals..
4. The Individuals that survive and reproduce are not just lucky - individuals with certain heritable traits are more likely to survive and reproduce than those that do not have the traits.
Also known as "Survival of the Fittest". Refers to the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits. This leads to evolutionary change.
-Effect on Phenotype: Favors one extreme phenotype, causing the average phenotype in the population to change in one direction. (Colored on Either Very Right or Very Left Side)
-Ex: Average body size increased in cliff shallows.
-Effect on Genetic Variation: Genetic Variation is Reduced.
-Effect on Phenotype: Favors Phenotypes near the middle of the range of phenotypic variation, maintains average phenotype. (Colored in Middle)
-Ex: Human Babies of average size are most likely to survive.
-Effect on Genetic Variation: Genetic Variation is Reduced.
-Effect on Phenotype: Favors extreme phenotypes at both ends of the range of phenotypic variation. (Colored on both sides)
-Ex: Black-bellied seed crackers with extreme beak size are most likely to survive.
-Effect on Genetic Variation: Genetic Variation is Increased.
-Effect on Phenotype: No single phenotype is favored in all population of species at all times. (Directly fills below line)
-Example: Guppies with rare color patterns are favored, changing the favored color pattern over time.
-Effect on Genetic Variation: Genetic Variation is maintained,
Why some deleterious alleles stick around
When Natural selection favors adaptive traits coded for by adaptive alleles, some deleterious alleles and traits get weeded out, others do not. Sickle Cell Anemia is a good example.
Sickle Cell Anemia - Genotype to Phenotype
A Allele: DNA ——> GAG CTC , RNA ——> GAG , Protein ——> GLU ——> GLU, GLU, HbA.
S Allele: DNA ——> GTG CAC, RNA ——> GUG , Protein ——> VAL ——-> VAL, VAL, HbS.
Sickle Cell Disease and Malaria
In heterozygous, (AS) only a few red blood cells are affected and the disease is not severe, but AS offers protection from Malaria. Thus, heterozygous people have an advantage over both homozygote genotypes. The S allele is therefore maintained in the gene pool - hidden in the heterozygote.
Prevalence of Sickle - Cell Anemia
-In some parts of Africa, about 4% of individuals are homozygous for HbS and have sickle cell disease.
-In the US, about 0.25% of African Americans are homozygous for the HbS allele and have sickle cell disease.
Evolution of one or more closely related species into different species; resulting from adaptations to different environmental conditions. When two or more species sharing a common ancestor become more different over time.
Process by which unrelated organisms independently evolve similarities when adapting to similar environments.
A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
Sexual Selection - Why do males usually have more elaborate traits to attract males than females?
-Females Produce relatively few young, fitness is limited not by access to mates, but access to resources to produce more eggs and keep young healthy.
-Male fitness is limit by how many females he can mate with.
-Eggs and babies are expensive, sperm are cheap.
-Cost of reproduction in males is low, high in females.
-Males can mate with as many females as they want, but there is a limit to how many offspring a female can have.
Asymmetry of Sex : The Bateman-Trivers Hypothesis of Sexual Reproduction Predicts
1. Females, but not males, should be choosy about mates since they invest a lot in each egg. The opposite should be true for males.
2. Males will compete with each other for mates.
3. Alleles that increase a male's attractiveness of success in male-male competition should increase in the population.
4. Sexual Selection should act more strongly on males than on females.
Sexual Dimorphism and Sexual Selection
-If sexual selection is associated to sexual dimorphism, sexual selection should act differently on males and females.
-Bateman and Trivers predicted that sexual selection will be a more potent mechanism in evolution of males.
-Bateman and Trivers prediction is based on the costs of gametes production for males and Females.
-Sexual Dimorphism: Males are larger than females.
Members of the sex subject to strong sexual selection will be competitive.
Members of the sex subject to weak sexual selection will be choosy.
Sexual Selection boils down to two main mechanisms
1. Female Choice
2. Male Competition
Female choose which males to mate with, how long to mate, and even whose sperm will fertilize her eggs. Some females can eject sperm from an undesirable mate.
Males compete for access to females, the amount of time spent mating with females, and even whose sperm gets to fertilize her eggs. For example, male damselflies scrub rival sperm out of the female reproductive tract when mating.
Females Choose Mates on the Basis Of:
1. Male Physical characteristics that signal the genetic quality of males.
2. Behavioral characteristics of males that indicate their ability to provide paternal care.
1. Males compete for the opportunity to mate with females.
2. Variation in reproductive success is high in males.
3. Variation in reproductive success is relatively low in females.
Intrasexual Selection Study Case: Marine Iguanas
-Males fight for breeding territories.
-Larger Males get the best Territories.
-Larger males have higher reproductive success than smaller males.
Intrasexual Selection: Case study, red-collared widow-bird.
-Females prefer males with longer tails.
-Long tails are favored by sexual selection.
Biological Fitness is best defined as
The ability of an individual to produce offspring that survive and reproduce, relative to other individuals in the population.
Cystic fibrosis is a genetic disorder in homozygous recessive (ff) humans that typically significantly reduces life expectancy. Over time, we would expect the f allele frequency to _____ for this trait.
If you say that a group squirrel has greater evolutionary fitness than another ground squirrel in the same population, you mean that the animal ________
Has more offspring that survives and reproduce themselves.
Relationship between Directional Selection and Genetic Variation
Directional Selection Reduces/ Decreases Genetic Variation.
In regions where malaria is prevalent, the S allele is beneficial because:
It causes red blood cells to distort, which makes them less hospitable to Plasmodium, the parasite that causes malaria.
Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer, or more, than this have reduced fitness. Which of the following terms best describes this situation?
Natural selection that increases the frequency of a favorable allele is called _______.
The wide variety of finches Darwin observed in the Galápagos was thought-provoking because they appeared to have descended from ________population. Today we regard this as an example of _______.
The same, Adaptive Radiation.
Which of the following is most likely to produce an African Butterfly species in the wild whose populations show two strikingly different color patterns?
Which of the following statements best summarizes evolution by natural selection as it is viewed today?
Evolution by natural selection is the differential survival and reproduction of the most-fit phenotypes.
Students also viewed
chapter 2 vocab (FOOOOOOOD)
chapter 13 karn
Somos Flex 1.2
Other sets by this creator
Ηomework Set #5
Homework Set #4
Recommended textbook solutions
Human Resource Management
John David Jackson, Patricia Meglich, Robert Mathis, Sean Valentine
Kenneth R. Miller, Levine
Clinical Reasoning Cases in Nursing
Julie S Snyder, Mariann M Harding
Hole's Human Anatomy and Physiology
David Shier, Jackie Butler, Ricki Lewis