Chapter 21 - Evidence and Mechanisms of Evolution Flashcards
What year is the beginning of the “Modern Era of Biology?”
1859
The Origin of Species was published by whom?
Charles Darwin
What did The Origin of Species contain?
Darwin’s theory of evolution
What did Darwin observe during his 5 year voyage on the Galapagos Islands?
He observed that the animals on each island differed from island to island.
What did Darwin theorize about the animals among the different islands of the Galapagos?
Theorized that some animals had come from mainland South America and then undergo changes on each of the islands.
What was the common opinion about living creatures during the 19th century?
Living creatures are immutable products of a sudden creation. They existed now in precisely the form in which they always existed.
What did Darwin’s observations from his visit to South America and Galapagos Islands disprove?
His observations disproved the fixity of species - the common opinion during the 19th century about living creatures being immutable products of a sudden creation.
What was the guiding factor that Darwin believed determined the course of change?
Natural Selection - the guiding factor that determines the course of change.
What is Evolution?
the Process in which the form and overall genetic structure of an organisms change with time.
What evidence did Darwin use to combat the static view of creationism?
1) Fossils, 2) Resemblances between living species, 3) Changes produced in domesticated plants and animals
What kind of bones were dug up in South America by Charles Darwin?
Darwin dug up bones of extinct GIANT ARMADILLOS and GROUND SLOTHS
What conclusion did Darwin come to when he reconstructed the skeletons of the fossils that he dug up?
Darwin came to the conclusion that the extinct version of the bones and the modern version of the bones were similar so they seemed to be related.
What did Darwin conclude from the resemblances of different species when compared?
Darwin came to the conclusion that resemblance suggested that all these species descended from a common ancestor, each with their own DISTINCTIVE MODIFICATION.
What is Artificial Selection?
A process in which humans consciously select FOR or AGAINST particular features in organisms.
(Example: the human may allow only organisms with the desired feature to reproduce or may provide more resources to the organisms with the desired feature. This process causes evolutionary change in the organism and is analogous to natural selection, only with humans, not nature, doing the selecting.)
What is Natural Selection?
The guiding force in evolution; one of the basic mechanisms of evolution, along with MUTATION, MIGRATION, and GENETIC DRIFT
What is the meaning of Immutable?
not subject to change
What is the meaning of Species?
Series of populations within which significant gene flow occurs under natural conditions, but which is genetically isolated; it is a kind of animal, plant, or organism; the basic unit of biological classification.
What is Population?
Localized group of individuals belonging to the same species.
What is Population Genetics?
Study of gene pools and genetic variation in biological populations.
What is Gene Pool?
All of the genes in a population or species, thus its genetic constitution. The alleles present and their relative frequencies.
What is Gene Flow?
Movement of alleles between populations through interbreeding; any movement of genes from one population to another and is an important source of genetic variation; also known as “migration”
What are the smallest units that can evolve?
POPULATIONS (not individual organisms) are the smallest units that can evolve.
What makes up a Scientific Name?
1) Genus and 2) Species Epithet
What is a Theory?
Generalization supported by MUCH evidence.
What kind of science (anatomy) did Darwin use to come to the conclusion of natural selection?
Darwin used the science of COMPARATIVE ANATOMY to come to a conclusion that all species had a common ancestor and this was support for the resemblances between living species.
What are (2) important facts that have to do with NATURAL SELECTION?
1) organisms vary, and these variations are inherited (at least in part) by their offspring. 2) organisms produce more offspring than can survive.
Describe Natural Selection’s creative force.
On average, offspring that vary most strongly in directions favored by environment will survive and propagate FAVORABLE VARIATION will therefore accumulate in populations by Natural Selection. Offspring that DO NOT vary most strongly in directions favored by environment will die.
Jean Baptiste de Lamarck
Pre-Darwinian; theorized (2) mechanisms that fostered evolutionary change: 1) PRINCIPLE OF USE & DISUSE 2) INHERITANCE OF ACQUIRED CHARACTERISTICS
Describe the PRINCIPLE OF USE AND DISUSE
Body parts grow in proportion to how much they are used and structures not often used get weaker and shrink.
(Example: muscles do grow larger through continued use; most structures don’t respond in a Lamarckian way; Lamarck refers to somatic changes)
Describe INHERITANCE OF ACQUIRED CHARACTERISTICS
Changes that an animal acquires during its lifetime are inherited by its offspring.
What German evolutionary biologist disproved Lamarck?
August Weismann (1834-1914)
August Weismann
German Evolutionary Biologist; disproved Lamarckism; Contributed the GERM PLASM THEORY - inheritance only takes place by means of the germ cells (the gametes or egg and sperm cells).
Is it possible for organisms of different species to reproduce?
Yes, BUT they have to be very similar species genetically for them to be able to reproduce, and it is likely that their offspring will be sterile, but not always, making it highly unlikely for the offspring to survive and reproduce.
What is the Hardy Weinberg Theorem?
Law of population genetics stating that in the absence of selection, nonrandom mating, and other conditions, heredity tends to stabilize allelic frequencies in a population.
It also predicts phenotypic ratios from genotypic ratios in a randomly mating population.
Who is Alfred Russel Wallace?
a British naturalist, explorer, geographer, anthropologist and biologist that also came up with the ideas of natural selection and evolution and pushed for Darwin to publish The Origin of Species.
What is Hardy Weinberg Equilibrium?
The Hardy-Weinberg theorem states that the frequency of the dominant allele and the frequency of the recessive allele for a given population will not change, given that a certain set of circumstances are met;
A model that provides a base line from which evolutionary departures take place. It is important in evolution since it tells use what will happen in a NONEVOLVING population.
It also describes a reference point with which to compare the frequencies of Alleles and genotypes of natural populations whose gene pools may be changing.
4)Random mating, no sexual selection 5)No natural selection
What does Hardy Weinberg Equilibrium describe?
It describes genetics of an idealized population. This situation never exists in nature (under natural conditions).
What are the (5) conditions that need to be met for Hardy Weinberg Equilibrium to be maintained?
1) Population is very large (infinitely large), so that there is NO GENETIC DRIFT.
2) Population is isolated. No immigration or emigration; no coming or going. (NO MIGRATION or GENE FLOW IN OR OUT)
3) No net changes in gene pool due to mutations. (NO MUTATIONS)
4) Mating is random. (NO SEXUAL SELECTION.)
5) All genotypes are equal to reproductive success. (NO NATURAL SELECTION)
What is Allele Frequency?
How common an allele is in a given population…
What is Genetic Drift?
A change in the population’s allele frequency due to chance.
Example: natural disaster
What does ‘p’ refer to in the Hardy Weinberg Theorem?
p = frequency of the dominant allele
What does ‘q’ refer to in the Hardy Weinberg Theorem?
q = frequency of the recessive allele
How can the Hardy Weinberg Theorem be used?
It can be used to measure if forces are acting on a population
What is the GENOTYPIC FREQUENCY FORMULA (Hardy Weinberg Equation)?
(p+q)² OR p² + 2pq + q² = 1
What does ‘p² ‘ refer to in the GENOTYPIC FREQUENCY FORMULA?
Frequency of homozygous dominant individuals; p² = Freq TT
What does ‘2pq’ refer to in the GENOTYPIC FREQUENCY FORMULA?
Frequency of heterozygous individuals; 2pq = Freq Tt
What does ‘q² ‘ refer to in the GENOTYPIC FREQUENCY FORMULA?
Frequency of homozygous recessive individuals; q² = Freq tt
What is the ALLELIC FREQUENCY FORMULA?
p+q=1
What are the genotypic frequencies?
Homozygous dominant (TT), heterozygous (Tt), homozygous recessive (tt)
What are the (2) kinds of evolution?
MICROevolution and MACROevolution
What is Microevolution?
Changes in gene frequency in a population from one generation to the next.
What is Macroevolution?
Evolution above the species level. The adaptive radiation of a lineage into many different niches is an example of macroevolution. Since evolutionary change above the species level, means that populations and species must be evolving, macroevolutionary change entails microevolutionary change.
What causes Microevolution?
1) Natural Selection 2) Mutation 3) Genetic Drift 4) Gene Flow and 5) Nonrandom Mating are all factors in microevolution
How does natural selection affect microevolution?
Natural Selection is the most common factor affecting genetic variability within a population caused by the unequal ability of individuals to produce viable, fertile offspring. Such differential reproduction results in a decrease in the frequency of some genes and the increase in frequency of others.
(Examples: English Peppered Moth, pesticide resistant insects, antibiotic resistant bacteria)
Scientific name for Moth
Biston betularia
How does mutation affect microevolution?
Mutations are generally harmful, but not always. They are rare and random (except in bacteria). Mutation directly changes the gene pool of a population through substitution of one allele for another or the deletion of an allele.
How does genetic drift affect microevolution?
Genetic Drift is a change in the gene pool of a SMALL POPULATION from on generation to the next that results from chance.
(2) Effects can produce populations small enough to experience genetic drift - BOTTLENECK EFFECT AND FOUNDER EFFECT
Bottleneck Effect
A disaster (i.e. earthquake, fire, flood) that drastically reduces the size of a population, killing its victims unselectively. THE BOTTLENECK EFFECT SETS MICROEVOLUTION IN PLACE
Founder Effect
A few individuals are separated from a larger population (perhaps on an island or in a lake). The smaller, separated population is unlikely to have the same proportion of genes as the larger population.
THE FOUNDER EFFECT LEADS TO MICROEVOLUTION.
What (2) effects result in microevolution?
Bottleneck effect and Founder effect
Gene Flow
When a population gains or loses alleles from the migration of fertile individuals (or the transfer of gametes) between populations
Nonrandom Mating
When individuals mate with close neighbors,promoting in breeding that causes the frequency of genotypes to deviate from the Hardy Weinberg Theorem.
What are the sources of Variation?
Mutation (rare and random, producing new alleles) and Recombination
What is Recombination?
A process in which pairs of chromosomes swap DNA with one another.
Nearly all genetic variation in a population results from new combination of alleles produced by sexual recombination (crossing over and random segregation during meiosis).
Polymorphism
2 or more distinct forms that regularly occur in a population
Natural populations are highly polymorphic (i.e. within a small population of snails there may be different coloring or coiling)
Most human populations are polymorphic in their blood types (A, B, AB, O, Rh system)
Polymorphism can be seen from protists (unicellular) to vertebrates (multicellular)
Some phenotypic polymorphisms (i.e. coloration) may have selective value (i.e. Land snail displays any one of 6 banding patterns)
What is the scientific name for a land snail?
Cepaea nemoralis
Balanced Polymorphism
The steady state preservation of variation in the population. (i.e. human blood types)
What is the scientific name for snow goose?
Chen caerulescens
Transient Polymorphism
A particular form is in the process of spreading through a population causing the relative proportion of phenotypes to alter. (i.e. english peppered moths)
What is the scientific name for the English peppered moth?
Biston betularia
Quantitative Variation
Traits that show continuous variation with no obvious patter of Mendelian segregation in their inheritence.
Traits are polygenic - influenced by variation at many genes. (i.e. height of adult males in human species)
Selection can act on quantitative traits to produce 3 different kinds of evolutionary response.
Stabilizing Selection
Phenotypes in the middle of the range of phenotypes are favored.
Favor average values of the trait and to disfavor extreme ones. (AVERAGE INDIVIDUALS ARE BEST ADAPTED)
i.e. after a storm, mortality is highest among largest and smallest birds, lowest among those of average size.
Directional Selection
Favors extreme value of the phenotype and cause the population average to shift toward it over time.
(NATURAL SELECTION PRODUCING EVOLUTIONARY CHANGE)
Disruptive Selection (Diversifying Selection)
Seemingly less common than the other 2 types; 2 different extreme phenotypes are simultaneously favored, but the average is disfavored.
Populations become bimodal.
Phenotypes will predominate (leading to balanced polymorphism).
What is Speciation?
Formation of a new species
What are the (2) types of Speciation?
1) Anagenesis (Phyletic Evolution) and 2) Cladogenesis (Cladistic speciation)
Anagenesis
When species changes so drastically over time that it becomes a different species and the ancestral species ceases to exist.
Cladogenesis
When 1 or more new species develop from an ancestral species, yet the ancestral species continues to exist.
(MORE COMMON and produces GREATER BIOLOGICAL DIVERSITY)
What is the scientific name for Horseshoe Crab?
Limulus polyphemus
Carboniferous Era
Prestwinchinella rotundala
Permian Era
Paleolimulus avitus
Jurassic Era
Limulus walchi
Present (Era)
Limulus polyphemus
Biological Species Concept
“Species are groups of actually or potentially interbreeding populations, which are reproduced isolated from such groups”
Morphological Species Concept
Group of organisms that differs in some morphological respect from all other groups.
Sympatric Speciation
Occurs when a subpopulation is reproductively isolated from its parent population.
This type of speciation usually results from a genetic change that produces a reproductive barrier between the parent population and the mutant offspring aka instantaneous speciation.
Instantaneous Speciation
The production of a single individual that for various reasons can’t interbreed with members of the species to which its parents belonged.
Polyploidy
Having more than 2 complete sets of chromosomes; instantaneous speciation causes polyploidy
Autopolyploidy
When the number of chromosomes doubles within a species
Allopolyploidy
Combining chromosomes from 2 different species
Sympatric Speciation
Very important in plant evolution
Isolating Mechanisms
Various isolating mechanisms maintain the integrity or purity of a species
Prezygotic Isolating Mechanisms
Before Fertilization; exert their effect before fertilization
Ecological Isolating Mechanisms (Prezygotic)
When populations live in different areas and don’t interact
Temporal Isolating Mechanisms (Prezygotic)
Occurs when mating or flowers takes place at different times of the day or different seasons
What is the scientific name for the American Toad?
Bufo americanus
What is the scientific name for Fowler’s Toad?
Bufo fowleri
Behavioral Isolating Mechanisms (Prezygotic)
Different species are not sexually attracted to each other. Different courtship displays and rituals. (i.e. fly flight patterns)
Mechanical Isolating Mechanisms (Prezygotic)
Occurs when structural differences in genitalia or flowers prevent copulation or pollen transfers
Gametic or Physiological Isolating mechanisms (Prezygotic)
When male and female gametes fail to fuse to form a zygote or cannot survive in the female reproductive tract of another species.
Post-zygotic Isolating Mechanisms
After fertilization; exert a role after fertilization occurs
Hybrid Inviability (Post-zygotic)
When hybrid zygotes don’t develop to sexual maturity
Hybrid Sterility (Post-zygotic)
When hybrids don’t produce viable gametes
Allopatric Speciation (Post-zygotic)
The development of a new species as a result of a physical barrier.
