Population Biology Exam 4

Mutation

Change in the genetic make up of an organism’s genomic sequence

Point Mutation

Deletions, substitutions, and insertions can affect ONE base pair or several nucleotides in sequence

Affect More than One Base Pair

Duplications, translocations, and inversions often affect entire chromosomes or even the organism’s genome

Inversion Mutation

Occurs when a chromosome breaks and, during the repair process, the segment flips and reconnects. Makes it unlikely that homologous chromosomes can cross over at any locus along the inversion. The inability to cross over means that the genes are tightly linked and form a sugergene (sex chromosomes are super genes)

Duplication Mutation

Can affect sets of chromosomes, these are commonly caused by nondisjunction during meiosis or mitosis. Create gametes that are diploid rather than haploid. Can create a polyploid (3X - triploid or 4X - tetraploid offspring). Triploids are less viable than tetrapods. Polyploid offspring are often incapable of breeding with their diploid parents and are new species. Die off in animals but common in plants.

Gene Duplication: Unequal Crossing-Over (meiosis)

Occurs as a consequence of incorrect synapsis - one chromosome ends up with a deletion and the other with a redundant duplicated stretch of DNA

Gene Duplication: Retrotransposition (transcription)

mRNA is a reverse transcribed into a double stranded DNA molecule which is incorporated into the genome

Homologous: Paralogous

They diverge within a genome

Homologous: Orthologous

They diverge after a speciation event

Artificial Selection

Traits that domesticated organisms have because of human desirability

Sexual Selection

A form of natural selection where the selective pressure arises from the preferences that individuals of one gender have for traits (physical traits, behaviors, etc.) of individuals of the other gender

Natural Selection

Refers to the evolution of traits in non-domesticated organisms because of their interaction with their environment

5 Observations of Natural Selection

1. All organisms have tremendous fecundity

2. But, population sizes are stable

3. Resources are limited

4. There is variation among individuals

5. The variation is heritable

3 Points of Natural Selection

1. There is differential success in reproduction

2. It occurs through an interaction between environment and the variability among organisms

3. It produces populations that are adapted to their environment

Four Postulates of Falsifiability and Natural Selection

1. Are individuals within a population variable

2. Are variations heritable, can they be passed from parents to offspring?

3. Is there differential reproductive success among individuals in a population

4. Is survival and reproduction non-random

Heritability

The proportion of the variation in a population that is due to variation in genes

Humans Cause Evolutionary Change

Population of pest insects evolved because the resistant insects had greater fitness (reproductive ability) than those without resistance. Differential reproductive success produced a population of insects that was better adapted to a field on which insecticide was sprayed.

Natural selection acts on individuals based on their _______ but affects the ________ of the population

phenotype, genetic makeup (allele frequencies)

Genes ________, individuals are ________ and populations _________.

mutate, selected, evolve

Natural Selection - directional

Operates through the interactions between organisms and their environment but produces better adapted populations

Phylogenetics

Study of evolutionary relatedness of organisms

Phylogenies

Based on traits that reflect common ancestries inferred from fossil, morphological, and molecular evidence

True or False: Phylogenies are always hypotheses?

True - Incomplete data, new data discoveries may contradict existing phylogeny, same traits can be interpreted differently

Taxonomy

Kingdom, Phylum, Class, Order, Family, Genus, Species

Node

Branch point

Root

Base of every tree

Phylogenetic trees

Diagrams that show evolutionary relationships, depicting common ancestors divergence points and the lineage of species over time.

Pedigree vs Phylogeny

Phylogeny represents evolutionary relationships between different groups of organisms, while a pedigree shows the ancestry within a family lineage, focusing on individual relationships between family members

Phylogenetic Systematics

The study of the diversification of living things both past and present, phylogenetic trees can be constructed based on shared characteristics

Cladogram

Depiction of patterns of shared characteristics among taxa using a tree without branch lengths that represent divergence

Clade

Within a cladogram defined as a group of species that includes an ancestral species and all of its descendants

Cladistics

The scientific process of grouping organisms together based on the proportions of characteristics they share

Monophyletic

Signifying that it consists of the ancestor species and all of its descendants, united by homologies/synapomorphies

Synapomorphies

Derived characteristics shared by all members of the clade

Apomorphy

Derived character, a novel trait that is unique to a species and all its descendants

Paraphyletic Clade

A grouping that consists of an ancestral species and some, but not all of the descendants

Symplesiomorphies

Primitive characteristics shared by some, but not all descendants, woudl create a paraphyletic clade

Plesiomorphy

An ancestral trait state, relative to a derived character

Polyphyletic

Grouping includes numerous species that lack a common ancestor

Homoplasies

Analogous structures (convergent evolution) body parts in different species that perform similar functions but have different evolutionary origins, unite polyphyletic groups

Analogous traits

shared by two or more species because of convergent evolution. These traits are not shared because of common ancestry

Homologous Traits

Found in two or more species because of descent from a common ancestor

Divergent Evolution

A process where closely related species or populations accumulate differences over time, which can lead to the development of new species

Parsimony Analysis

Assumes that the best phylogeny is formed by the tree with the fewest evolutionary changes

Ingroup

Information about characters are used to build evolutionary relationships among species

Outgroup

The number of changes in the ingroup is compared to a species outside of the group we are trying to classify

Speciation

Process that creates diversity

Anagenesis

The transformation of one species into another over time

Macroevolution

Origin of new taxonomic groups

Cladogenesis

Branching evolution, is the budding of one or more new species from a parent species (increases biological diversity)

Prezygotic Barrier

Keep a zygote (fertilized egg) from forming. Includes habitat isolation, behavioral isolation (courtship displays), temporal isolation, mechanical incompatibility, genetic incompatibility

Postzygotic Barriers

Affect the zygote. Includes reduced hybrid viability (spontaneous abortion of hybrid/weak hybrid), reduced hybrid fertility (ex. mules), and hybrid breakdown (hybrids are reproductive, could mate with either parent species or each other but offspring are not)

Reproductive Barriers Occur

Before mating, between mating/fertilization, and after fertilization

What are the Three Modes of Speciation?

Allopatric, parapatric, and sympatric

Allopatric Speciation

Geographic separation of populations restricts gene flow (ex. geology: mountain ranges, glaciers, land bridges, or splintering of lakes. migration: individuals colonize a new, geographically remote area)

Parapatric Speciation

The populations are adjacent to one another. Occurs because of an abrupt change in habitat with no barrier to dispersal (uncommon)

Sympatric Speciation

Two or more species evolve within geographically overlapping populations.

Autopolyploid

Individuals result from mating of two parents of the same species and are tetraploid

Allopolyploid

Polyploid individuals can occur when individuals are produced by the matings of two different species

Gradualism

Big changes occurred as the accumulation of many small ones

Punctuated Equilibrium Model

Rate of speciation is not constant, species undergo rapid modification when they first diverge, once established species they change litte

Proximate Causality

How a something happens right now in real time. Physiologically a movement as a behavioral response to a stimulus

Ultimate Causality

Why something happens - evolutionary time scale, because it increased fitness in the past

Direct Choices

Females pick males based on some aspect of him

Indirect Choice

Males fight and winner gets to mate with female