BIO 152 Exam 1 Vocabulary and People

biogeography (Alfred Russell Wallace)

Similar species tend to be found geographically close together.

Associated with Darwin as well.

common ancestry (Darwin)

The idea that if you trace back the lineages of living species far enough back in time, those species will converge to shared, common ancestors.

homologies (Darwin)

Structures that have deep, underlying similarities between species.

Homologous traits

Same structure, different function. Goes along with homologies and common ancestry studied by Darwin.

nested structure

If taxonomic groups shared common ancestry at different times in the past, it is expected that taxonomies would be structured with groups within groups: multiple genera within each family, multiple families within each order, etc. This nesting pattern is consistent with the idea of a diversifying process, beginning from an ancestor and radiating like the branches of a tree that don’t overlap.

What evidence did Darwin use to justify his theory of common ancestry?

Homologies, transitional fossils, and nested structures of taxonomies

polymorphic

• The existence of two or more distinct physical forms, phenotypes, or genetic variants within the same population of a species

  • Ex. White flower population producing a purple flower (genetic variation). This can happen via gene mutation.

• When more than one allele is found at a given locus in a population

evolution

Change in the genetic composition of the population, and it happens when you have a polymorphic population.

fixed or fixation

• The change in frequency of a polymorphic population, when variants in a population become extinct.

• The loss of all variants except one from a population

• An allele that has a frequency of 1.0 in a population

natural selection (Darwin)

Implies that whichever genetic variants make an organism better equipped for the pressures of its environment will tend to increase in frequency in populations over time. Therefore, populations should get better adapted to their environments over time and fixation will occur for these traits. Also, the process of allele frequency change due to fitness variation among genotypes at that locus 

transition fossil

Fossil taxa that have some, but not all, of the derived traits of a living group

What is evolution?

Descent with modification that has a pattern (recorded in anatomy, fossils, embryos, genomes, etc.) and process of change (that is observable and testable). It also constitutes a change in the genetic composition of a population over time.

Why do we study evolution?

• Unifies biology

  • It brings together fields like genetics, developmental biology, molecular and cell biology, paleontology, etc.

• Practical applications

  • Combating disease and predicting the spread of pathogens

  • Fighting drug resistance in bacterial strains

  • Improving agriculture through development of pest-resistant crops

  • Supports conservation efforts

Aristotle

• Species were fixed (i.e. an elephant is an elephant forever)

• He arranged them on scala naturae which created a hierarchy of life forms (“higher” and “lower” species”

• He believed that geography changes (water forms change over time and so does land)

William Paley

• Natural Theology is what he is known for

• He had this idea that a watch implies a watchmaker in the same way that something is complex because of its creator

  • Life is static but it was created by an entity

• Naturally occurring complex structures (like an eye) are comparable to human inventions (like a telescope)

Carolus Linnaeus

• Created the binomial classification system (…Order → Family → Genus → Species) in Systema Naturae

• He separated organisms into three kingdoms: mineral (geology), vegetable (botany), and animal (zoology)

• “Nature does not proceed by leaps and bounds” states that there are bigger differences for a species outside of its genus

• He saw species as part of the divine plan, but that Earth and species were unchanging

What was Carolus Linnaeus’s classification system in order?

• Imperium (Empire) - everything

• Regnum (Kingdom) - animal, plant, mineral

• Classis (Class) - in the animal kingdom, there were six: mammals, birds, amphibians, fishes, insects and worms

• Ordo (Order) - subdivisions of class

• Genus - subdivision of order

• Species - subdivision of genus

• Varietas (Variety) - species varieties or “sub-species”

James Hutton

• Father of modern geology

• Proposed uniformitarianism

• He believed that natural laws that apply today must also have applied in the past (as in life is not really changing), geological “deep time” (which is geological timescale of Earth’s history that proves the Earth is really really old), and that catastrophic/supernatural events are not required to explain the history of the Earth.

Uniformitarianism (James Hutton)

Changes in the Earth’s crust have resulted from the action of continuous and gradually acting processes, such as erosion and sedimentation

Thomas Malthus

• Economist that tried answering the question why people go to war

• He created a curve (featured) that shows populations grow much faster that resources, and once that at a certain threshold (after the two lines cross), available resources will limit population growth

• This curve later ties in with Darwin’s idea of natural selection, in that species produce more offspring than their environment can support (differential survival and reproduction)

Jean Leopold Nicolas Frederic, Baron Cuvier

• The founder of paleontology

• Developed the study of fossils by expanding the Systema Naturae to include distinct forms such as dinosaurs

• Observed the pattern that fossils and living organisms become increasingly dissimilar as we go back in time

• Suggested that the fauna of the past was once dominated by reptiles, not mammals, based on dinosaur bones

• Key to the development of the idea that extinction is a widespread process

Directional selection

Removes genetic variation in populations while random mutation replenishes that variation

Null model

A model that predicts the data you should expect to see if a process is not working—meaning, when a particular causative agent is not impacting the situation.

Hardy-Weinberg Principle

A null model stating that if no selection, drift, gene flow, or mutation occur, and if mating is random with respect to the gene in question, then allele frequencies will not change from one generation to the next and genotype frequencies will be in the proportions p2, 2pq, q2, where p and q are the frequencies of two alleles at that gene.

Assortative mating

Mate choice based on similarities or dissimilarities in phenotype.

Inbreeding

Mating among relatives.

Gene pool

A concept used in predicting the results from random matings among all of the individuals in a population, by supposing that all gametes are tossed into "pool" and then drawn out at random to produce offspring.

Genetic bottleneck

The phenomenon in which a population lineage shrinks to a small size for a period, causing that population to lose genetic variation

Genetic drift

Random change in allele frequencies in a population over time

Genetic load

The frequency of deleterious alleles that have accumulated in a population

Beneficial mutation

A new allele that enhances the fitness of organism

Deleterious mutation

A new allele that decreases organismal fitness

Directional selection

Selection that arises when one allele consistently raises fitness; eventually the beneficial allele is expected to become fixed in the population

Mutation

A change in a gene sequence; arises independent of the needs of the organism.

Neutral mutation

A new allele with neither a beneficial nor a deleterious effect

Relative fitness

The fitness of a given genotype divided by the fitness of a reference genotype, which relative fitness is assigned to be 1.0

Carrier

An individual who is heterozygous for a disease 

Overdominant selection

Selection in which heterozygote genotypes have the highest fitness

Trans-specific polymorphism

A set of alleles that are shared between closely related species; they arose before speciation and were maintained as polymorphisms

Underdominant selection

Selection in which heterozygote genotypes have the lowest fitness

Continuous traits

Genes not controlled by a single locus, but instead multiple loci, that have a bell shaped curve in which the intermediate trait is usually expressed

Allele frequency

In a population, the proportion of all alleles at a locus that are of a particular type

Hardy-Weinberg Law

The law that, when a few key assumptions hold, makes it is possible to predict the genotype frequencies in a population for the next generation, based on the allele frequencies in the current generation 

Locus

A place in the genome where alleles reside; in diploids, each individual has two alleles per locus

Phenotype

The physical and behavioral characteristics of an organism that result from the interaction of the organism’s genotype and its environment

Genotype

Genetic makeup of an organism

Population

A group of interbreeding organisms

Selfing

When an organism reproduces with itself, providing both the egg and sperm components

Allopatric speciation

Speciation driven by geographic isolation

Assortative mating

The phenomenon in which individual organisms tend to mate with other organisms with trait values like theirs

Stabilizing selection

Selection that disfavors extreme trait values and favors trait values towards the center of the trait distribution

Biological Species Concept

The view that species are defined by the ability of their members to reproduce with one another and to be unable to reproduce with the members of other species

Clinal variation

Gradual changes in traits as a function of geographical separation

Discrete variation

Genetic variation among geographically separated populations, where each population contains genetically similar individuals

Extrinsic reproductive isolation

The phenomenon in which two organisms are unable to reproduce due to geographic separation

Intrinsic reproductive isolation

The phenomenon in which two organisms are no longer able to reproduce, even when they are allowed to encounter one another

Phylogenic Species Concept

The view that species are clades (monophyletic groups), like other in the taxonomic hierarchy (genera, subspecies, etc.), that biologists have chosen to assign to the species rank for practical reasons

Speciation

The splitting of an ancestral species into descendant species

Sympatric speciation

Speciation without geographical separation, driven by assortative mating within a population

Disruptive selection

Selection that favors trait values at both extremes of the trait value distribution

Heritability (h²)

The fraction of the variation in a population that can be explained by genetics

Response to selection, r

The amount the mean trait value in a population changes after one generation

Stabilizing selection

Selection that disfavors extreme trait values and favors trait values towards the center of the trait distribution

Standard deviation

Square root of the variance

Variance

A measure of the spread of the distribution of a trait values in a population (technically, the sum of the squared deviations from the mean value)

Altruistic behavior

Actions (or tendencies to act) that result in the organism exhibiting the behavior lowering its own fitness while increasing the fitness of other organisms within its population

Exaggerated secondary sexual selection

Dramatic traits in an organism that lower the organism’s viability but evolve because they are favored by sexual selection

Polygamy

The phenomenon in which one male can mate with many females 

Runaway sexual selection

the phenomenon in which secondary sexual characteristics become exaggerated due to feedback between male traits and female preferences (or, more rarely, female traits and male preferences)

Covergent evolution.

The phenomenon observed in phylogenetic trees where the same trait evolves separately in more than one lineage; although they appear similar, these traits are not homologous

Homologous

A descriptor of a character shared in separate species that was inherited from the common ancestor of those species 

Principle of parsimony

The idea that given multiple alternative hypotheses, the most likely hypothesis is the one that makes the fewest assumptions; in relation to phylogenies, parsimony favors the scenario that invokes the minimum number of evolutionary changes (character loss/gain)

Reversal

The phenomenon in which an ancestral trait was lost and then re-evolved along a lineage

Separate ancestry

The alternative hypothesis to common ancestry, which proposes that each living taxon has an independent origin

Anoxygenic photosynthesis

The reduction of carbon dioxide to organic molecules using light energy in which something other than water is the electron donor and oxygen gas is not released

Autogenous hypothesis for eukaryotes

The theory that mitochondria and nucleus both evolved within the same eukaryotic lineage

Cyanobacteria

A clade of bacteria characterized by its ability to perform oxygenic photosynthesis

Endosymbiosis

The phenomenon in which a prokaryotic cell comes to live and divide within a host cell

Endosymbiotic theory for eukaryotes

The theory that mitochondria are derived from endosymbiotic bacteria taken up by the host cell whose genome is found in the eukaryotic nucleus

Eukaryotic cells

A category of cells characterized by an outer membrane and many internal membrane-bound compartments including the mitochondria and nucleus 

Inside-out model

A theory for development of eukaryotic internal compartments that suggests that the outer plasma membrane of a prokaryotic ancestor was pushed outward and ultimately fused to create the cytoplasm and plasma membrane of eukaryotes.

LUCA (last universal common ancestor)

The most recent ancestor of all known life

Organelle

Membrane-bound compartment of a eukaryotic cell

Outside-in model

A theory for development of eukaryotes that starts with the production of vesicles within the cytoplasm by internalization

Oxygenic photosynthesis

The reduction of carbon dioxide to organic molecules using light energy in which water is the electron donor and oxygen gas is released

Prokaryotic cells

A category of cells characterized by an outer membrane containing no internal membrane structures

Metazoan

a multicellular animal that is made up of cells differentiated into tissues and organs.

Opisthokont clade

a broad group of eukaryotes that includes Animals and Fungi.

Bilateral symmetry

body plan where an organism has a head and a tail, a left and right, and an up and down.

Cambrian Period

a period of rapid diversification of complex animal life when all major bilaterian phyla appeared.

Evolutionary arms race

this occurs when two interacting species develop adaptations and counter-adaptations to each other.

Red Queen Principle

an evolutionary concept where species must continually adapt and evolve to survive, or they risk extinction.

Arthropods

invertebrates with segmented bodies, an exoskeleton, and paired, jointed appendages.

Tetrapods

vertebrates with four limbs.

Amphibians

cold-blooded vertebrates with scale-less, moist skin who spend part of their life in water and part on land.

Amniotes

animals characterized by having an egg with an amnion (a thin membrane that surrounds the fetus within the amniotic sac)

Admixture

The mating of two individuals from genetically distinct group

Diurnal

The characteristic of being active during the day

Introgression

The transfer of genetic information between species