Chapter 22

Descent with Modification

three striking observations about life

1. the striking ways in which organisms are suited for life in their environment

2.the many shared characteristics (unity) of life

3. the rich diversity of life

Aristotle

Carolus Linnaeus

developed the binomial format for naming species

strata

layers of rock that essentially house fossils

Georges Cuvier

-advocated catastrophism

-inferred that extinctions must have been a common occurrence in the history of life through his examinations of fossils

catastrophism

James Hutton

Charles Lyell

created the principal of uniformitarianism

uniformitarianism

states that mechanisms of change are constant over time

Jean Baptiste de Lamarck

Developed the principles:

-use and disuse: the idea that parts of the body that are used become larger/stronger while those that are not used deteriorate

-inheritance of acquired traits: an organism could pass these modifications to its offspring

Charles Darwin

-"On the Origin of Species by Means of Natural Selection"

-natural selection

-adaptations

-descent with modification

adaptations

natural selection

a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits

artificial selection

descent with modification

characteristics present in an ancestral organism are altered (by natural selection) in its descendants over time as they face different environmental changes

homology

similarity resulting from common ancestry

homologous structures

convergent evolution

the independent evolution of similar features in different lineages

analogous

where species share features because of convergent evolution

biogeography

the geographic distribution of species

continental drift

the slow movement of Earth's continents over time

microevolution

evolution on its smallest scale

Gregor Mendel

-wrote about inheritance in pea plants

-proposed a particulate model of inheritance in which organisms transmit discrete heritable units (genes) to their offspring

genetic variation

differences among individuals in the composition of their geners or other DNA segments.

discrete characters

quantitative characters

average heteryozygosity

the average percentage of loci that are heterozygous

geographic variation

differences in the genetic composition of separate populations

cline

a graded change in a character along a geographic axis

population

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

gene pool

consists of all copies of every type of allele at every locus in all members of the population

Hardy-Weinberg principle

Conditions for Hardy-Weinberg Equilibrium

1. No mutations

2. Random mating

3. No natural selection

4. Large population

5. No gene flow

genetic drift

founder effect

when a few individuals become isolated from a larger population, & the smaller group establishes their own population, whose gene pool differs from the source population

bottleneck effect

a severe drop in population. by chance alone, certain alleles may be overrepresented among survivors, others underrepresented, or some completely absent.

effects of genetic drift

1. significant in small populations

2. can cause allele frequencies to change at random

3. can lead to a loss of genetic variation within populations

4. can cause harmful alleles to become fixed

gene flow

relative fitness

directional selection

occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting a population's frequency curve for the phenotypic character in one direction or the other. common when a population's environment changes or when members of a population migrate to a new and different habitat.

disruptive selection

stabilizing selection

acts against both extreme phenotypes and favors intermediate variants. this mode of selection reduces variation and tends to maintain the status quo for a particular phenotypic character

sexual selection

sexual dimorphism

a difference between the two sexes in secondary sexual characteristics (size, color, behavior, etc)

intrasexual selection

individuals of one sex (usually females) are choosy in selecting their mates of the other sex

neutral variation

differences in DNA sequence that do not confer a selective advantage or disadvantage

balancing selection

occurs when natural selection maintains two or more forms in a population.

heterozygote advantage

frequency-dependent selection

the fitness of a phenotype depends on how common it is in the population

why natural selection cannot fashion perfect organisms

1. selection can act only on existing variations

2. evolution is limited by historical constraints.

3. adaptations are often compromised.

4. chance, natural selection, and the environment interact

speciation

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

microevolution (II)

changes over time in allele frequencies in a population

macroevolution

the broad pattern of evolution above the species level

biological species concept

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

reproductive isolation

hybrids

offspring that result from an interspecific mating

prezygotic barries

block fertalization from occurring

postzygotic barriers

may contribute to reproductive isolation after the hybrid zygote is formed

habitat isolation

two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though they are not isolated by obvious physical barriers

temporal isolation

species that breed during different times of the day, different seasons, or different years cannot mix their gametes.

behavioural isolation

mechanical isolation

mating is attempted but morphological differences prevent its successful completion

gametic isolation

sperm of one species may not be able to fertilize the eggs of another species.

reduced hybrid viability

the genes of different parent species may interact in ways that impair the hybrid's development or survival in its environment

reduced hybrid fertility

hybrid breakdown

morphological species concept

characterizes a species by body shape and other structural features.

ecological species concept

phylogenetic species concept

defines a species as the smallest group of individuals that share a common ancestor, forming one branch in the tree of life

allopatric speciation

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

sympatric speciation

speciation occurs in populations that live in the same geographic area

polyploidy

where a species originates from an accident during cell division that results in extra sets of chromosomes

autopolyploidy

is an individual that has more than two chromosome sets that are all derived from a single species

allopolyploidy

a form of polyploidy that results in interbreeding between species

hybrid zone

a region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

reinforcement

reinforcement of reproductive barriers (weak, unfertile, etc offspring)

punctuated equilibria

describes a period of apparent stasis punctuated by sudden change.

phylogeny

the evolutionary history of a species of group of species

systematics

a discipline focues on classifying organisms and determining their evolutionary relationships

taxon

the named taxonomic unit at any level of the heirarchy of the evolutionary tree

branch points

(phylogenetic tree)

each branch point represents the divergence of two evolutionary lineages from a common ancestor

sister taxa

(phylogenetic tree)

groups of organisms that share an immediate common ancestor, and hence are each other's closest relatives

rooted

(phylogenetic tree)

a branch point within the tree represents the most recent common ancestor of all of the taxa in the tree

basal taxon

(phylogenetic tree)

refers to a lineage that diverges early in the history of a group

polytomy

homoplasies

analogous structures that arose independently

molecular systematics

the discipline that uses date from DNA and other molecules to determine evolutionary relationships

clades

each of which includes an ancestral species and all of its descendants

monophyletic

- "single tribe"

- a taxon is only equivalent to a clade if it is monophyletic, signifying that it cnsits of an ancestral species and all of its descendants.

paraphyletic

"beside the tribe"

consists of an ancestral species and some, but not all of its descendants

polyphyletic

"many tribes"

includes taxa with different ancestors

shared ancestral character

a character that originated in an ancestor of the taxon

shared derived character

an evolutionary novelty unique to a clade

outgroup

a species or group of species from an evolutionary lineage that is known to have diverged before the lineage species we study (ingroup)

maximum parsimony

a principle that states we should first investigate the simplest explanation that is consistent with the facts

maximum likelihood

states that given certain probability rules about how DNA sequences change over time, a tree can be found that reflects the most likely sequence of evolutionary events

orthologous genes

are those found in different species, and their divergence traces back to the speciation events that produced the species

paralogous genes

neutral theory

much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by natural selection

horizontal gene transfer

a process in which genes are transferred from one genome to another through mechanisms such as exchange of transposable
elements and plasmids, viral infection, and perhaps fusion of organisms

mixotrophs

a protist that combines photosynthesis and heterotrophic nutrition

endosymbiosis

algae

photosynthetic protists

(red and green)

secondary endosymbiosis

chromalveolata

(protist)

alveolates

protists with membrane bound sacs (alveoli) just under the plasma membrane.

dinoflagellates

conjunction

a sexual process in which two individuals exchange haploid micronuclei but do not reproduce

stramenopiles

protists that include some of the most important photosynthetic organisms.

"hairy" flagellum and "smooth" flagellum

diatoms

unicellular algae that have a glass-like wall made of silicia.

major component of phytoplankton

brown algae

multicellular, most marine

thalli

closest relative to land plants

thalli

(thallus)

describes an algal body that is plantlike

holdfast, blades, stipe

holdfast

a rootlike anchor that holds algae in place

stipe

a stem like structure of thallus algae

blades

leaflike structures of thallus algae

alternation of generations

the alternation of multicellular haploid and diploid forms

heteromorphic

means that the sporophytes and gametophytes are structurally different

(algae)

isomorphic

where the sporophytes and gametophytes look similar, but differ in chromosome number.

(algae)

pseudopodia

extensions that may bulge from almost anywhere on the cell surface

red algae

most are multicellular, includes the major "seaweeds"

green algae

structured most like the chloroplasts of land plants, 

chlorophytes

green algae

charophyceans

green algae that is most closely related to land plants (more so than chlorophytes)

symbionts

an organism that lives in a symbiotic relationship (mutually beneficial)

unikonts

includes protists that are closely related to fungi and animals

producers

sporopollenin

a layer of durable polymer that prevents exposed zygotes from drying out

an adaptation green algae developed to move on land

apical meristem

sporangia

multicellular organs that produce spores

sporocytes

archegonia

female gametangia

gametangia

multicellular structures that produce gametes

antheridia

male gametangia

cuticle

vascular tissue

bryophytes

non-vascular plants

gymnosperms

"naked seed" plants

seeds not enclosed in chambers

consists of all flowering plants

seeds develop inside ovaries, which mature into fruits/flowers

gametophore

a gamete producing structure

bryophyte

liverworts, hornworts, mosses