Foundations Of Bio, 2 - Exam 2

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Scientific theories have two components:

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1) A process

2) A pattern

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The pattern component of a theory describes:

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how things are in nature; facts; a series of observations

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The process component of a theory describes:

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a mechanism that produces a pattern

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A species:

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defined as an evolutionarily independent population

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The three theories for defining a species:

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1) Biological species concept

2) Morphospecies concept

3) Phylogenetic species concept

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Biological species concept:

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a species is defined as a population that is reproductively isolated

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Types of prezygotic isolation:

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1) Temporal

2) Behavioral

3) Mechanical

4) Gametic

5) Habitat

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Types of postzygotic isolation:

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1) Hybrid viability

2) Hybrid sterility

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Morphological species concept:

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Based on the morphologies (structural traits) of populations

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Phylogenetic species concept:

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identifies evolutionarily independent lineages by mapping the evolutionary history os populations

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Monophyletic group (clade; lineage):

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consists of an ancestral group and all of its descendants on a given phylogenetic tree

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Synapmorphy:

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a trait found in certain groups of organisms that exists in no others (can be genetic, structural, or developmental)

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The smallest monophyletic group:

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species!

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Speciation begins when:

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gene flow between populations is reduced or eliminated

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Physical isolation of populations occurs in two ways:

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(both types are allopatric)

1) Dispersal

2) Vicariance

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Vicariance:

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a physical splitting of habitat

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Allopatric speciation:

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begins with physical isolation

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Populations in allopatry:

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live in different areas

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Biogeography:

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the study of how species and populations are distributed geographically

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Sister species:

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taxa that are each others' closest relative

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Sympatry:

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when populations or species live in the same geographic area, close enough to interbreed

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Sympatric speciation:

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speciation that occurs even though gene flow is possible

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Polyploidy:

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when an individual has more than two sets of chromosomes

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Autopolyploidy:

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gametes with uneven chromosome numbers are produced by the same species

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Allopolyploidy:

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different species mate and the number of chromosomes in the offspring doubles

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Reinforcement:

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natural selection for traits that isolate populations (disruptive selection, kinda)

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Hybrid zone:

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a geographic area where interbreeding occurs and hybrid offspring are common

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Mechanisms of sympatric speciation (two):

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1) Disruptive selection

2) Polyploydation

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Possible outcomes of Secondary contact between populations (five):

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1) Fusion of the populations

2) Reinforcement (disruptive selection)

3) Hybrid zone formation

4) Extinction of one population

5) Creation of new species

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Phylogeny:

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the evolutionary history of a group of organisms

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A phylogenetic tree:

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shows the ancestor-descendant relationships between populations/species

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Branch:

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represents a population over time

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Node:

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the point where two branches diverge

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Phenetic approach:

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when researchers use gene sequences to compute overall "genetic distance" between two populations

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Cladistic approach:

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inferring trees based on synapmorphies

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Ancestral trait:

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a trait that existed in an ancestor

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Derived trait:

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a trait that is present in an organism but not present in its ancestor - derived

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Homology:

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traits that are similar in different populations because they came from a shared ancestor

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Homoplasy:

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when traits are similar in different populations but did NOT come from a common ancestor

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Convergent evolution:

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when selection for similar traits occurs in different populations, but these traits are not present in ancestral species (homoplasy)

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Parsimony:

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the most likely explanation is the one with the fewest changes

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Outgroup:

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a species or group that is closely related to the monophyletic group being studied, but is not being studied itself

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SINEs:

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Short Interspersed Nuclear Elements (transposable elements)

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Adaptive radiation:

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when a single lineage produces many descendant species that have many different ecological niches

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The three characteristics of adaptive radiation:

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1) Occurs within monophyletic groups

2) Rapid speciation

3) New niches evolve

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The two things that trigger adaptive radiation:

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1) New resources

2) New ways to exploit resources

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Fauna:

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a collection of animal species (fossils)

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The three main faunas:

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1) Doushantuo - microscopic

2) Ediacaran - small, soft-bodied

3) Burgess Shale - diverse, large, hard-bodied

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What triggered the Cambrian Explosion (four elements):

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1) Higher O2 levels

2) The evolution of predation

3) New niches beget more new niches

4) Hox genes led to new bodies

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The two types of resources that led to the adaptation of land plants:

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1) Sunlights

2) CO2

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Cuticle:

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a wax layer on some land plants that covers the above ground portion of the organism, and prevents it from drying out

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Stomata:

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is a structure of all land plants (except liverworts) that consists of a pore surrounded by two guard cells

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The two challenges in overcoming gravity:

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1) transporting water to cells that aren't in contact with the soil

2) Becoming strong enough to withstand gravity and wind

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Lignin:

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the defining feature (six-carbon polymer) of vascular tissue

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Tracheids:

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long, narrow vascular tissue

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Vessel elements:

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short, wide vascular tissues

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Vessel elements are only found in (two types of organisms):

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1) Gnetophytes

2) Angiosperms

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The two main adaptations that led to efficient reproduction of land plants:

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1) Gametes were produced in multicellular structures

2) The embryo was retained on the parent

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Gametangia:

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the places where sperm and eggs are produced in all land plants (except angiosperms)

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The sperm-producing gametangium:

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anthridium

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The egg-producing gametangium:

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archegonium

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Embryophyta:

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plants that retain their embryos and nourish them

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The life cycle of a land plant has two phases:

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1) haploid - gametophyte

2) diploid - sporophyte

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Seed:

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a structure that includes an embryo surrounded by a food source and a tough coat

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_______ are like seeds, but they lack _________:

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Spores; nutrients

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Stamen:

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where microsporangia develop in angiosperms

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Carpel:

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where ovaries are found in angiosperms

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Endosperm:

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the nutritive tissue formed when a sperm cell fuses with two nuclei in the female gametophyte

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Sepals and petals:

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modified leaves that enclose sepals and carpels

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Pollination:

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the transfer of pollen from one individual's stamen to another's carpel

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Pollinator:

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an animal that disperses pollen

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Fruit:

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a structure that is derived from the ovary and contains at least one seed

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The three key adaptations for the diversification of angiosperms:

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1) Vessels

2) Flowers

3) Fruits

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The two main categories for angiosperms:

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1) Monocots

2) Dicots

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Cotyledon:

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the first leaf formed in an embryonic plant

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Monocots:

Dicots:

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1) Have a single cotyledon

2) Have two cotyledons

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Fossil record:

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consists of all the fossils that have been found

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Extant species:

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species that are living today

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Transitional feature:

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a trait in a fossil species that is intermediate between those of older and younger species

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Vestigial trait:

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a reduced or underdeveloped structure in one population that is similar to a functional trait in another population

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Phylogeny:

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a family tree of populations or species

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The three types of homology:

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1) Genetic - DNA sequences

2) Developmental - Embryonic

3) Structural - morphological

(genetic leads to developmental leads to structural)

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The main sources of evidence for evolution:

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1) The fossil record

2) Vestigial traits

3) Homologous traits

4) Populations are constantly changing