CH 23 & 25: Evolution Flashcards
What is evolution?
Heritable change in one or more characteristics from one generation to the next
What is microevolution?
changes in a single gene in a population over time
What is macroevolution?
formation of new species or groups of species
What influence did the Uniformitarianism hypothesis from geology have on Darwin’s theory of evolution?
- Slow geological processes lead to substantial change
- Earth was much older than 6,000 years
What did Darwin call his theory of evolution?
Descent with modification
What influence did Thomas Malthus, an economist, have on Darwin’s theory of evolution?
Only a fraction of any population will survive and reproduce
Population growth limited by:
•Famine
•War
•Disease
Survival & reproduction are key components of natural selection
What is descent with modification, evolution, based on?
Variation within a given species
•Traits heritable –passed from parent to offspring
•Genetic basis was not yet known
Natural selection
•More offspring produced than can survive
•Competition for limited resources
•Individual with better traits flourish and reproduce
What animal did Darwin study on the galapagos that influenced his theory of evolution?
Finches and their beak size
- finches from south american mainland flew to galapagos with variety of beak sizes (ie. variation)
- natural selection weeded out beak sizes that weren’t conducive to eating galapagos seed and nuts
What evidence is there for the theory of evolution?
-Fossil record
-Biogeography
-Convergent evolution
-Selective breeding
-Homologies (morphology/DNA)
•Anatomical
•Developmental
•Molecular
What is the evidence of evolutionary change in the fossil record?
- Evolution of the horse ~ ex of how evolution involves adaptation to changing environments
- changes in size, foot anatomy, and tooth morphology
- Changes because natural selection producing adaptations to changing global climates
- Large dense forests replaced with grassland
- Run faster, eat tougher food
What is the evidence of evolutionary change in biogeography?
Study of the geographical distribution of extinct and modern species
•Isolated continents and islands evolve their own distinct plant and animal communities
•Closely related species living in isolation become divergent
•Endemic–naturally found only in a particular location
What is the evidence of evolutionary change in convergent evolution?
Two different species, without common ancestor, show similar characteristics because they occupy similar environments
•Suggests adaptation to the environment
Examples:
•Antifreeze proteins in different, very cold water fish
What is the evidence of evolutionary change in Selective breeding?
Programs and procedures designed to modify traits in domesticated species
•Also called artificial selection
•Nature chooses parents in natural selection while breeders choose in artificial selection
•Made possible by genetic variation
What is the evidence of evolutionary change in homology?
Fundamental similarity due to descent from a common ancestor
Homology may be any inherited type of character
•Anatomical
•Developmental
•Molecular
What is the evidence of evolutionary change in anatomical homology?
Same set of bones in the limbs of modern vertebrates has undergone evolutionary change for many different purposes
•Homologous structures are derived from a common ancestor
•Vestigial structures are anatomical structures that have no function but resemble structures of ancestors
What is the evidence of evolutionary change in developmental homology?
Species that differ as adults have similarities during embryonic stages
•Presence of gill ridges in human embryos indicates humans evolved from an aquatic animal with gill slits
•Human embryos have long bony tails
What is the evidence of evolutionary change in molecular homology?
Similarities in cells at the molecular level show that living species evolved from a common ancestor
•same type of gene is often found in DNA of diverse organisms
•Sequences of closely related species tend to be more similar to each other than to distantly related species
What are Homologous Genes?
Two genes derived from the same ancestral gene
What are Orthologs?
Genes in different species that evolved from a common ancestral gene by speciation
-The genes have similar functions
What is a Gene Family?
A set of Several similar genes formed by duplication of a single original gene
What is a Paralog?
two or more homologous genes derived from the same ancestral gene at different locations
-The genes do different functions
When does a homologous gene become an ortholog?
When mutations accumulate enough so the two genes are not identical anymore
What is Macroevolution?
evolutionary changes that create new species and groups of species
What is a species?
Group of organisms that maintains a distinctive set of attributes in nature
What characteristics are commonly used to identify a species?
1) Morphological Traits
2) Ability to Interbreed (reproductive isolation)
3) Molecular Features
4) Ecological Factors
5) Evolutionary Relationships
What are Morphological Characteristics? What are the drawbacks to using it to identify a species?
- Physical Characteristics of organism
- How many traits to consider? Same species can look different. Different species can look similar.
What is the ability to interbreed? What are the drawbacks to using it to identify a species?
- Reproductive isolation prevents one species from successfully interbreeding with another species
- Difficult to determine in nature, some species’ can interbreed but don’t, Doesn’t apply to asexual species, can’t be applies to extinct species
What are Molecular Features? What are the drawbacks to using it to identify a species?
Compare features to identify similarities/differences among different populations
- DNA sequences within genes
- Gene Order along chromosomes
- Chromosome structure
- Chromosome Number
Difficult to draw the line when separating groups
What are Ecological Factors? What are the drawbacks to using it to identify a species?
Factors related to organism’s habitat
- Different species display similarities in habitat
- Same species display differences in habitat
What are the different species concepts?
Biological Species Concept: species can interbreed
Ecological Species Concept: Each species occupies ecological niche
Evolutionary Lineage Concept: Species based on separate evolution of lineages
What is speciation?
formation of a new species
What is the cause of speciation?
accumulation of genetic changes that cause enough differences to create a separate species
What are the mechanisms of speciation?
Reproductive Isolation
- Prezygotic Barriers: prevent formation of zygote
- Postzygotic Barriers: block development of viable zygote
What are the types of Prezygotic barriers?
Habitat Isolation: Geographic barrier prevents contact
Temporal Isolation: Reproduce at different times of the day or year
Behavioral Isolation: Behaviors important in mate choice
What are the types of Postzygotic barriers?
Hybrid Inviability: Fertilized egg can’t proceed past early embryo
Hybrid Sterility: Interspecies hybrid viable but sterile
Hybrid Breakdown: Hybrids viable and fertile but have genetic abnormalities
How does Speciation occur?
Cladogenesis: Division of a species into two or more species
-Requires gene flow between populations to be interrupted
What are the types of Cladogenesis?
Allopatric Speciation
-When some members of species become geographically separated. Most Common.
Sympatric Speciation
-Members of specie diverge into two or more different species even though there are no physical barriers to interbreeding
How can allopatric speciation occur when a small population moves to a new location that is geographically separated?
Natural selection
-Alters genetic composition of population leading to adaptation to new environment
Adaptive Radiation
-Single species evolves into array of descendants that differ greatly
What are the mechanisms of Sympatric Speciation?
Polyploidy
-Automatic b/c extra genes cause sterility
Adaptation to Local Environment
-geographic area may have variation so members diverge to occupy different local environments
Sexual Selection
-Eventually don’t want to mate with other members of your species that vary slightly from yourself
What is a hybrid zone?
zone where two population can interbreed
-geographic separation is not complete
Once gene flow though hybrid zone is greatly diminished, the two populations are reproductively isolated
What are the two main hypotheses for the pace of speciation?
Gradualism and Punctuated Equilibrium
What is Gradualism?
Each new species evolves continuously over long spans of time
-Large phenotypic differences due to accumulation of many small genetic changes
What is Punctuated Equilibrium?
Tempo of speciation more sporadic
-long periods of equilibrium and the short rapid bursts of change
Do species evolve slowly or quickly?
Both, fossil records provide evidence for both
-Generation time influences speed of evolution (ie. microbial vs. humans)
