Macroevolution

Taxonomy

Classification made by Carolus Linnaeus based on structural similarities

Kingdom level

largest and most inclusive level

species level

the most specific grouping

taxonomic groups from species to domain

domian, kingdom, phylum, class, order, family, genus, species

taxon

taxonomic unit at any level of hierachy

phylogeny

study of the evolutionary relationships among a group of organisms

phylogenetic tree

construct that represents a branching “tree-like” structure which illustrates the evolutionary relationships of a group of organisms; represents the TRUE evolutionary history

cladogram

used to represent a HYPOTHESIS about evolutionary history of a group of organisms

how many lineages should come from 1 node?

2; if there are more it indicates an unresolved pattern of divergence or polytomy

sister taxa

groups or organisms that share an immediate common ancestor (branches can rotate and represent the same phylogeny)

clade

any taxon that consists of all the evolutionary descendants of a common ancestor

true clade

monophyletic group that contains a common ancestor and all of its descendants

paraphyletic group

one that has a common ancestor but does not contain all of the descendants

polyphyletic group

does not have a unique common ancestor for all the descendants

anagensis (phyletic change)

the accumulation of changes in one species that leads to speciation over time, evolution of a whole population; when certain changes have accumulates the ancestral population is considered extinct

cladogenesis

the budding of one or more new species from a species that continues to exists; results in biological diversity and involves the physical separation of the group to allow them to evolve separately

homologous features

any feature shared by two ore more species and inherited from a common ancestor

ancestral trait

the original shared trait

derived trait

the trait found in newly evolved organisms

analogous features

those that are similar in structure but are not inherited from a common ancestor; not used in establishing phylogenies

why do analogous structures exist?

similar selection pressures & evolutionary reversals

molecular clock hypothesis

among closely related species, a given gene usually evolves at a reasonably constant rate; these mutation events ca be used to predict times of evolutionary divergence, so the protein encoded by the gene accumulates amino acid replacements at a relatively constant rate

what are the rules that apply to reconstructing a phylogeny?

maximum likelihood & maximum parsimony

maximum likelihood

states that when considering multiple phylogenetic hypotheses, one should take into account the one that reflects the most likely sequence of evolutionary events given certain rules about how DNA changes over time

maximum parsimony

states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts

outgroup

group that is closely related to the taxa being examined but is less closely related, typically having a lot of 0’s in a chart

species

a group of interbreeding organisms that can produce viable, fertile offspring in nature

macroevolution

evolution on a scale of separated gene pool; focus on change that occurs at or above the level of species

microevolution

smaller evolutionary changes that are typically described as changes in allele frequencies within a species or population

asexual species

don’t exchange genes but are recognizable groups that typically evolve from sexual species

ring species

a connected series of neighboring populations, each of which can interbreed with closely sited or related populations, but for which there exists at least two “end” populations in the series

what is true of end populations?

they are too distantly related to interbreed, though there is a potential gene flow between each “linked” species; non-breeding but genetically connected

subspecies

a group within a species that had become somewhat physically and genetically different from the rest of the group, but are still similar enough to interbreed with the rest of the species

limited interbreeding

occurs when two different species will breed with each other in captivity, but not naturally in nature, therefore they are not the same species (ex. liger)

allopatric speciation

speciation occurs because a given group has been separated from the parent group, usually because of a geographic separation as time goes by

sympatric speciation

speciation occurs even though the two groups are still living in the same area

Once two populations are isolated geographically from one another, if the two groups become sympatric again, what are the two things that can result?

1. they become separate species because they can no longer interbreed

2. they can still interbreed, so they remain the same species

adaptive radiation

the process of one species inhabiting a new area and evolving into several new species; can be caused by the founder effect, varying selection pressures, varying mutations; commonly involves islands

how does speciation occur?

prezygotic & postzygotic barriers

prezygotic

isolation mechanisms that prevent the formation of a zygote by preventing mating or fertilization

postzygotic

keep two populations distinct, thus they are no longer the same species and can no longer interbreed to produce viable, fertile, offspring in nature

ecogeographic isolation (pre)

two populations have become so specialized for survival in different environments, that once the geographical barrier is removed the two species will never again interbreed as one species; prevent gene flow

habitat isolation (pre)

two species have developed a preference for two different habitats. even if the species become sympatric, the probability that they will meet and mate is low

seasonal isolation (pre)

the two species have developed different times of the year to mate

behavioral isolation (pre)

if courtship behavior changes during separation, then sympatric mating will not occur and two new species are formed

mechanical isolation (pre)

there is a physical or biological structure that prevents mating

gametic isolation (pre)

the gametes are shed simultaneously but something physical or chemical prevents the sperm from fertilizing the egg

developmental isolation (post)

if fertilization occurs, the development of the embryo can be irregular and is thus spontaneously aborted

hybrid inviability

a hybrid is produced, but often does not make it to reproductive age because it is week, irregular

hybrid sterility (post)

some hybrids produce superior offspring but the offspring are sterile

selective hybrid elimination

the elimination or hybrid breakdown occurs if two species are sympatric and can hybridize, and their offspring can reproduce

what are two possibilities of selective hybrid elimination?

1. the hybrids are as viable or as fit as the parents and gene flow will occur and the two species will become one again

2. The hybrids are weaker or have lower fitness than the parents and will be selected against

how does natural selection intertwine with selective hybrid elimination?

natural selection will select for those individuals that will mate with their own species and the hybrids will die out. The competition between the two species will cause character displacement

parapatric speciation

is the evolution of geographically adjacent populations into distinct species. Divergence occurs despite limited interbreeding where the two diverging groups come into contact

sympatric speciation

has no geographic constraint to interbreeding: something within the environment that keeps a single species separated into two or more distinct groups

why is the ocean blue?

water molecules tend to absorb reddish light, leaving the blue light to travel towards the depths of large bodies of water

what happens when water is clouded by particles

sediment particles are good at absorbing bluish light, so when the sun shines on cloud water, blue light is present near the surface, but just a few meter down, most of the blue light will have been absorbed and mainly red light will penetrate

What does the physics of light effect?

how the animals living in the world’s oceans, lakes, and rivers are able to find food and each other, which can impact their evolution

polyploidy

instant speciation which occurs most often in plants

polyploid cells & organisms

those containing more than two paired (homologous) sets of chromosomes

autopoluploidy

the occurrence in which the number of chromosomes double in the offspring due to total non-disjunction during meiosis

allopolyloids

polypoids with chromosomes derived from different species

chromosomal rearrangements

large-scale mutations involving changes in chromosome structure, including deletion, duplication, inversions, and translocation which can lead to speciaition

gradualism / phyletic gradualism

model of evolution which theorizes that most speciation is slow, uniform and gradual.

punctuated equilibrium

most species will exhibit little net evolutionary change for most of their geological history, reaming in an extended state called stasis: occurs after some crisis in the environment or reduction in population size

big bang theory

proposes the universe began in a single instant 13-15 billion years ago, and in that instant all existing energy appeared and exploded outward from a single point

what was the first element produed

hydrogen, with traces of helium and lithium