Lecture Exam 1

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Chapter 27, Speciation

If two different populations do not interbreed in nature, or if they fail to be able to hybridize, they are considered different species under the biological species concept..

Prezygotic genetic isolation is when different species cannot mate.

Temporal: Breed at different times.

Habitat: Breed in different habitats.

Behavioral: Courtship displays differ.

Gametic barrier: Egg and sperm are incompatible.

Mechanical: Actual reproductive structures are incompatible.

Postzygotic is when hybrids cannot live to produce children.

Hybrid viability: Death as embryos.

Hybrid sterility: Sterile hybrids.

Cannot determine different species in fossils or species that reproduce asexually.

Morphological species concept identifies species via morphological traits.

Can determine two different species when there's only one with different phenotypes.

Cannot identify cryptic species.

Morphological species are subjective.

Phylogenetic species concept identifies species based on the phylogenetic species.

Few well-estimated phylogenetic trees are available.

Speciation occurs when two populations become genetically isolated and then diverge from each other.

Allopatric speciation is when populations diverge from geographic isolation.

Dispersal is when population splits off from itself to another area and develops adaptation.

Vicariance is when geography splits a population in two or more populations.

Sympatric speciation occurs when two species live in the same geographic area, through external events and internal events.

External events include disruptive selection through things like temporal events.

Internal events include polypolidity.

Autopolyploid: When a mutation doubles the amount of chromosomes.

Allopolyploid: When two different species breed and produce offspring with two different sets of chromosomes.

When two species come into contact there can be reinforcement, hybrid zones, and speciation via hybridization.

Reinforcement is when hybrids have a lower fitness than parents.

Hybrid zones are where hybrids become common.

There are new species through hybridization.

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Chapter 28, Phylogenetics and the History of Life

Phylogenetic trees are the evolutionary history of organisms, usually determined by synapomorphies.

Occam's Razor is used to determine which tree most likely reflects the actual tree.

Homoplasty is when traits are similar due to reasons other than common ancestry.

Homology occurs when traits are shared due to common ancestry.

Adaptive radiation is when a single lineage produces many descendant species with a wide range of adaptive forms.

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Green Algae and Land Plants

Plants provide ecosystemic services and provide humans with fuel, fiber, food, building materials, and medicines.

Biologists study green algae and land plants by analyzing morphological traits, the fossil records, and phylogenetic trees.

Key morphological traits are similar between green algae and land plants.

Chloroplasts containing photosynthetic pigments chlorophyll a and b and beta carotene.

Similar arrangements of thylakoids.

Cell walls, sperm, and peroxisomes are similar.

Chloroplasts synthesize starch as a storage product.

There are also differences between land plants; nonvascular plants lack cells that conduct water and nutrients from one side of the plant to another, seedless vascular plants are exactly what they sound like, and seed plants (which always have vascular tissue).

Land plants suggest that land plants evolved from multicellular freshwater green algae.

Fossil records reveal that first, simple land plants evolved about 475 million years ago and then diversified.

Monophyletic trees reveal that there was a major divergence in how seeds develop, either naked (gymnosperms) or capsuled (angiosperms).

The transition to land was a long one.

Plants adapted to dry conditions and intense sunlight by developing cuticle and stomata, a way to absorb UV light, and the development of vascular tissue. Reproduction was allowed via producing gametes in a protected structure, nourishing the embryos instead of shedding them, alternation of generations, and the development of seeds, flowers, fruits, and the pollination of plants via animals.

Monocots and dicots were identified.

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