BIOL 191: Exam #1 STEVENSON UNR

Evolution

"descent with modification"; the view that all organisms are related through descent from another ancestor that lived in the remote past

Fossils

remains or traces of organisms from the past, usually found in sedimentary rock (one of three main rock groups)

Strata

a layer or a series of layers of rock in the ground

Ancestral species

species descended from ancestors found in lower strata layers

Derived species

species that branches off from another species found in the upper layers of the strata

Adaptation

the process; any alteration in the structure or function of an organism or any of its parts that results from natural selection, by which the organism becomes better fitted to survive and multiply in its environment

Adaptations

the traits of an organism that change

Artificial selection

the process of humans modifying other species by selecting or breeding individuals wth desired traits

Darwin's Observation #1

Members of a population often vary in their inherited traits

Darwin's Observation #2

All species can produce more offspring that the environment can support, and many of these offspring fail to survive and reproduce

Darwin's Inference #1

Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals

Darwin's Inference #2

The unequal ability of individuals to survive and reproduce will lead to the acclimation of favorable traits in the population over generations

Chapter 19 Concepts

1. The Darwinian revolution challenged traditional views of a young Earth by unchanging species

2. Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life

3. Evolution is supported by an overwhelming amount of scientific evidence

Homology

similarity from common ancestor

Homologous structures

anatomical resemblances that represent variations on a structural theme present in a common ancestor

Vestigial structures

remnants of features that served important functions for an organism's ancestor

Convergent evolution

the evolution of similar (analogous) features in distantly related groups

Analogous traits

arise when groups independently adapt to similar environments in similar ways

Biogeography

the geographic description of species which provides evidence of evolution

Phylogeny

evolutionary history of a species or group of related species

Systematics (phylogeny)

classifies organisms and determines their evolutionary relationships

Taxonomy

ordered division and naming of organisms

Binomial

the two-part scientific name of a species

Genus

the first part of a species' two-part scientific name

Taxonomic groups

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

Phylogenetic trees

depiction of evolutionary relationships in branching structures used by systematists; represents a hypothesis about evolutionary relationships

Branch point

represents the divergence of two taxa from a common ancestor on a phylogenetic tree

Sister taxa

groups that share an immediate ancestor on a phylogenetic tree

Rooted tree

includes a branch to represent the most recent common ancestor of the entire phylogenetic tree

Homologies

phenotypic and genetic similarities due to shared ancestry

Analogy

similarity due to convergent evolution

Homoplasies

analogous structures or molecular sequences that evolved independently

Cladistics

classifies organisms by common descent

Clade

a group of species that includes an ancestral species and all its descendants

Molecular clock

uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change

Horizontal gene transfer

the movement of genes from one genome to another; plasmids, viral infection, fusion of organisms

Microevolution

a change in allele frequencies in a population over generations (time)

Genetic variation

the variation in the DNA sequence of each organisms' genomes

The Hardy-Weinberg Principle

Describes a population that is not evolving

The Hardy-Weinberg Equation

The Hardy-Weinberg Equilibrium conditions

The condition for non evolving populations are rarely met in nature:

1. No mutations

2. Random mating

3. No natural selection

4. Extremely large population size

5. No gene flow

In real populations, allele frequencies do change

Genetic drift

Describes how allele frequencies fluctuate unpredictably from one generation to the next; due to randomness and chance

The Founder Effect

occurs when a few individuals become isolated from a larger population

The Bottleneck Effect

can result from drastic reduction in population size due to a sudden environmental change; the resulting gene pool may no longer be reflective of the original population's gene pool

Gene flow

the movement of alleles among populations

Adaptive evolution

an increase in the frequency of alleles that improve fitness due to natural selection

Directional selection

favors individuals at one end of the phenotypic range

Disruptive selection

favors individuals at both extremes of the phenotypic range

Stabilizing selection

favors intermediate variants and acts against extreme phenotypes

Sexual selection

natural selection for mating success; certain phenotypes are correlated with better overall genotype

Sexual Dimorphism

marked differences between the sexes in secondary sexual characteristics

Speciation

the process by which one species splits onto two or more species

Macroevolution

refers to broad patterns of evolutionary change above the species level

Biological species concept

states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring

Reproductive isolation

the existence of biological barriers that impede two species from producing viable, fertile offspring

Pre-zygotic barriers

block fertilization by:

- Impeding different species from attempting to mate

- Preventing the successful competition of mating

- Hindering fertilization if mating is successful

Types of pre-zygotic barriers

Habitat, Temporal, Behavioral, Mechanical & Gametic Isolation

post-zygotic barriers

prevent the hybrid zygote from developing into a viable, fertile by:

- Reduced hybrid viability

- Reduced hybrid fertility

- Hybrid breakdown

Reduced hybrid viability

Genes of different parent species may interact and impair the hybrid development or survival

Reduced hybrid fertility

even if hybrids are vigorous, they may be sterile

Ex. Donkey + Horse = Mule

Hybrids

the offspring of crosses between different species

Hybrid breakdown

some first-generation hybrids are fertile, but when they mate with another species or either parent species, offspring of the next generation are feeble to sterile

Ex. strains of cultivated rice accumulating bad alleles

Morphological species concept

defines a species by structural features

(applies to sexual and asexual species, but relies on subjective criteria)

Ecological species concept

views a species in terms of its ecological niche

(applies to sexual and asexual species and emphasizes the role of disruptive selection)

Phylogenetic species concept

defines a species as the smallest group of individuals on a phylogenetic tree (i.e. the smallest branch)

Allopatric speciation

gene flow is interrupted when a population is divided into geographically isolated subpopulations

Sympatric speciation

speciation that takes place in populations that live in the same geographic area

Polyploidy

the presence of extra sets of chromosomes due to accidents during cell division

Autoploidy

an individual with more than two chromosome sets, derived from one species

Allopolyploid

a species with multiple sets chromosomes derived from different species

Punctuated equilibria

periods of apparent stasis punctuated by sudden change; speciation can occur rapidly or slowly, can result from changes in few or many genes

Half-life

the time required for half the parent isotope to decay

Stromatolites

oldest known fossils; rocks formed by the accumulation of sedimentary layers on bacterial mats

Plate techtonics

a theory explaining the structure of the earth's crust and many associated phenomena as resulting from the interaction of rigid (lithospheric) plates that move slowly over the underlying mantle

Mass extinction

the result of disruptive global environmental changes; when the rate of extinction (caused by changes in a species' environment) increases dramatically

Adaptive radiation

the evolution of many diversely adapted species from a common ancestor

List and briefly describe Darwin's two observations and two inferences on natural selection.

(Ch. 19)

- Observation #1: Members of a population often vary in their inherited traits

- Observation #2: All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce

- Inference #1: Individuals whose inherited traits give them a higher prob of surviving and reproducing in a given environment tend to leave more offspring than other individuals

- Inference #2: This unequal ability of individuals to survive & reproduce will lead to the accumulation of favorable traits in the population over generations

List and briefly describe four conditions that must be present to maintain the Hardy-Weinberg equilibrium. Additionally, state what is occurring if the equilibrium is determined to be broken? (Ch. 21)

The condition for non evolving populations are rarely met in nature:

- No mutations: without DNA mutations, a species is unable to become introduced to new genetic material which inhibits natural selection from occurring

- Random mating

- No natural selection: natural selection can not occur because the affected species has no variation in genes resulting in a lack of competition for new desirable traits

- Extremely large population size: a large pop means the population is not affected by evolutionary causation in their environment (because of their ability to survive and flourish)

- No gene flow: no genetic variation or random mating leads to a lack of gene flow resulting in a population unable to evolve

If the frequencies of alleles in a population are changing (if the equilibrium is determined to be broken) it can be concluded that the population is evolving

List and briefly describe five reproductive barriers that may exist between species. Additionally, state whether each reproductive barrier is pre-zygotic or post-zygotic. (Ch. 22)

PREZYGOTIC BARRIERS block fertilization from occurring by :

HABITAT ISOLATION: Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

- Aquatic vs. terrestrial garter snakes

TEMPORAL ISOLATION: Species that breed at different times of the day, different seasons, or different years cannot mix their gametes

- Ex. mating season of skunk species

BEHAVIORAL ISOLATION: Courtship rituals and other behaviors unique to a species are effective barriers

- Ex. blue-footed boobies display

MECHANICAL ISOLATION: Morphological differences prevent successful mating

- Ex. snail species' reproductive anatomy

GAMETIC ISOLATION: Sperm of one species may not be able to fertilize eggs of another species

- Ex. sea urchin gametes

POSTZYGOTIC BARRIERS prevent the hybrid zygote from developing into a viable, fertile by:

REDUCED HYBRID VIABILITY: Genes of the different parent species may interact and impair the hybrid development or survival

REDUCED HYBRID FERTILITY: Even if hybrids are vigorous, they may be sterile

- Ex. Donkey + Horse = Mule

HYBRID BREAKDOWN: Some first-generation hybrids are fertile, but when they mate with another species or either parent species, offspring of the next generation are feeble or sterile

- Ex. strains of cultivated rice accumulating bad alleles