BIO199 - Exam #1

Characteristics of organisms

composed of one or more cells, carry out metabolism, transfer energy with ATP, encode hereditary info in DNA

Systematics

study of evolutionary relationships (how are organisms related? how did life get to be the way it is?)

Phylogeny

hypothesis about patterns of relationship among species

Descent with modification

Darwin envisioned that all species were descended from a single common ancestor

Evolution is not always divergent

it is often convergent

Cladistics - ancestral characteristic

similarity that is inherited from the most recent common ancestor of an entire group (and is shared with the larger group)

Derived characteristic

similarity that arose more recently and is shared only by a subset of the species (shared with the most recent common ancestor by not with the larger group)

In cladistics

only shared derived characters are considered informative about evolutionary relationships

Plesiomorphies (plesio - morph)

near, shape - ancestral states

Symplesiomorphies (sym)

with - shared ancestral states

Symplesiomorphies reflect

character states inherited from a distant ancestor, do not imply species are closely related

Clade

evolutionary unit that refers to a common ancestor and all descendants

Synapomorphy

derived character shared by clade members

Cladogram

depicts a hypothesis of evolutionary relationships

Apomorphy

a novel character or character state that has evolved from its ancestral form S

Synapomorphy

an apomorphy shared by two or more taxa and is therefore hypothesized to have evolved in their most recent common ancestor

Synapomorphy implies

homology

All homologues are synapomorphics but

not all synapomorphics are homologues

Outgroup

species or group of species that is closely related to (but not a member of) the group under study is designated as the outgroup = do not always exhibit ancestral condition

When the group under study exhibits multiple character states, and one of those states is exhibited by the outgroup

then that state is ancestral and other states are derived

Simple cladogram

a nested set of clades, each characterized by its own synapomorphies

Amniotes

a clade for which evolution of an amniotic membrane is a synapomorphy

Homoplasy

a shared character state that has not been inherited from a common ancestor (convergent evolution)

Statistical approach

start with an assumption about the rate at which characters evolve

Molecular approach

rate of evolution of a molecule is a constant through time, divergence in DNA can be used to calculate the times at which branching events have occurred

Taxonomy

the science of classifying things

Classification

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

Monophyletic group

includes the most recent common ancestor of the group and all its descendants (clade)

Paraphyletic group

includes the most recent common ancestor of the group, but not all its descendants

Polyphyletic group

does not include the most recent common ancestor of all members of the group

Biological species concept (BSC)

defines species as groups of interbreeding populations that are reproductively isolated P

Phylogenetic species concept (PSC)

species is a population or set of populations characterized by one or more shared derived characters

BSC can only be applied to

sexual species

PSC can be applied to both

sexual and asexual species

Homologous structures

derived from the same ancestral source

Homologous structure example

dolphin flipper and horse leg

Homoplastic structures

are not derived from the same ancestral source

Homoplastic structures example

wings of birds and dragonflies

3 conditions of natural selection

phenotypic variation must exist in the population, must lead to differences among individuals in lifetime reproductive success, must be genetically transmissible to the next generation

When the environment changes,

natural selection often favors different traits in a species

Peppered moths

body color controlled by single gene, black individuals have the dominant allelle → frequency of dark moths increased near industrialized centers

Artificial selection

change initiated by humans, operates by favoring individuals with certain phenotypic traits, allowing them to reproduce and pass their genes on to the next generation

Repeating artificial selection

results in changes in the characteristics of a domesticated population over time

Domestication

human-imposed selection has produced a variety of cats, dogs, pigeons, and others

Experimental selection -example

imposed selection on most aspects of fruit fly

Fossils are

the preserved remains of once-living organisms

Geologists determine the absolute age of rocks using

isotopic dating

Vestigial structures

have no apparent function, but resemble structures ancestors possessed

Vestigial structures example

appendix in humans, boa constrictors have hip bones and rudimentary hind legs

Pseudogenes

Fossil genes; traces of previously functioning genes, when a trait disappears = does not just vanish from the genome

Pseudogenes example

icefish have colorless blood that doesn’t contain hemoglobin, but contain the DNA to create hemoglobin

“Evolution is not solidly demonstrated”

“just a theory”, scientists use they word “theory” differently than general public

“There are no fossil intermediates”

many intermediates have been found since Darwin’s time

The intelligent design argument

too complex for a random process, natural selection is not random, but it is not direction

“Evolution violates the Second Law of Thermodynamics”

Things become more disorganized, Earth is not a closed system and energy is constantly added from the Sun

“Proteins are too improbable”

Probability of hemoglobin as random event, can’t argue backwards = what are the odds of students having the birthdates they do in class

“Natural selection cannot explain major changes”

no scientist has evolved a fish into a frog, artificial selection has produced differences more distinctive than those between wild species

Complexity argument

intricate machinery of cell cannot be explained by evolution from simpler stages, natural selection can act on a complex system b/c at every stage of its evolution, the system functions

Fitness is

the ability of an individual to produce offspring

Individuals with high fitness

produce many more surviving offspring than do others in the population

Adaptation

a trait that increases the fitness of an individual in a particular environment

Hardy-Weinberg principle

used to calculate allele frequencies

Hardy-Weinberg equilibrium

no mutation takes place, no genes are transferred to or from other sources (no gene flow), mating is random, population size is large, no selection occurs

Mutation

ultimate source of genetic variation, makes evolution possible

Gene flow

movement of alleles from one population to another (animal physically moves into new population)

Nonrandom mating

phenotypically similar individuals mate

Genetic drift

change in allele frequencies in a population due to change (sampling error)

Gene flow is

random with respect to fitness

Genetic drift is prevalent in

small populations

Founder event

a group starts a new population in a new era (allele frequencies differ from the source population)

Bottleneck population

sudden decrease in population size (disease outbreaks, natural disasters)

Directional selection

changes average value of a trait

Epistasis

interactions between genes

Stabilizing selection

reduces genetic variation in a trait (average value of a trait does not change over time

Disruptive selection

increases variation in a trait (has opposite effect stabilizing selection

Speciation

the formation of new species

Balancing selection

maintains variation in a trait (occurs when no single allele has a distinct advantage

Heterozygote

favored over homozygotes

Intersexual selection

mate choice

Intrasexual selection

where individuals compete for mates

Handicap hypothesis

only genetically superior mates survive with a handicap such as a long tail that is a hinderance in flying

Sexual dimorphism

refers to any trait that differs between males and females of the same species

Female’s reproductive strategies

evaluate a male’s quality and then decide whether to mate

Fundamental asymmetry of sex

results from the fact that, in most species, females invest more in their offspring than do males

Sperm competition

selects for features that increase probability that a male’s probability that a male’s sperm will fertilize the eggs

Sensory exploitation

evolution in males of a signal that exploits preexisting biases

Negative frequency-dependent selection

rare phenotypes favored by selection, preyed upon less frequently

Positive frequency-dependent selection

favors common form, tends to eliminate variation, oddballs stand out

Gene flow can be

spread beneficial mutation to other pop but can impede adaptation by continual flow of inferior alleles from other populations

Sympatric species

live in the same place, are distinctive entities, phenotypically different, utilize different parts of the habitat, behave separately

Reproductive isolation

do not mate with each other or do not produce fertile offspring

Prezygotic isolating mechanisms

mechanisms that prevent formation of a zygote

Postzygotic isolating mechanisms

mechanisms that prevent proper functioning of zygotes after they form

Ecological isolation

species occur in the same area, occupy different habitats and rarely encounter each other

Behavioral isolation

species differ in their mating rituals

Temporal isolation

species reproduce in different seasons or at different times of the day

Mechanical isolation

structural differences between species prevent mating

Prevent of gamete fusion

gametes of one species function poorly with gametes of another species or within the reproductive tract of another species

Hybrid infertility

hybrid embryos do not develop properly, hybrid adults do not survive in nature, or hybrid adults are sterile or have reduced fertility

Behavioral isolation reasons

visual signals, sound production, chemical and electrical signals