Lecture 4 Flashcards
What are 3 useful categories of evolution?
- microevolution
- speciation
- macroevolution
explain microevolution
changes within a species:
- not controversial, even among most creationist publications
- observed in nature and in laboratory experiments
- includes variation and natural selection!
explain speciation
formation of new biological species:
- also shown to occur in nature and laboratory, but still controversial to some
explain macroevolution
- changes above species or genus level
- interpretation of fossil record
- the origin of complex adaptations (ex. eyes)
How does resistance arise in antibiotic resistant strains in bacteria, and pesticide resistance in insects and weedy plants?
- mycobacterium tuberculosis
- this is natural selection at work, sorting variations that arise spontaneously by mutation
What can natural selection act on?
- can act on any heritable trait
ex. a trait with genetic variation
What are 3 examples of the presence of different variations a gene (alleles), or whole DNA sequences?
- physical or structural differences: Body or body part size, shape, colours, patterns
- physiological and biochemical differences: proteins, structural and regulatory; enzymes, hormones
- developmental patterns (embryology
What are the 2 conditions for natural selection that are met for any trait in a population?
- there is heritable (genetic) variation
- the variation results in a fitness differential (=advantage or disadvantage to reproduction in the current environment)
Then that trait will evolve in that population by natural selection
What is evolutionary fitness?
- not survival alone, but an individual’s contribution of genes to the next generation
ex. reproductive success compared to others
What are the two fitness concepts and what are they?
- physical fitness: physically fit but not evolutionarily fit if no children produced…
- biological evolutionary: # of surviving offspring determine fitness, genes contributed to next generation (population gene pool) determines fitness
What is an example of unplanned selection by humans?
- the average size of Atlantic Cod has declined due to fishing pressure on the largest fish. Smaller female cod also reproduce at a younger age, and produce fewer eggs than earlier populations
- trophy hunting of largest big horn sheep is reducing the mean size of male horns in population
What are homologous traits
- similar structures in descendant organisms can be explained as resulting form inheritance from a common ancestor
- homology of forelumb bones, among any others, of tetrapods: vertebrates with 4 limbs
- homology can be obvious or not
homology between humans and who are obvious?
- chimpanzees
-we have similar hands (bones, muscles, ligaments, etc.) - foot differences greater (grasping big toe in chimps_ but basic bone, muscle, and other structures are similar
When we are thinking of feet, what is an example of homology that is not obvious with humans?
- elephant’s foot pads
- elephants walk on high heels, with the heel elevated on a large fat pad.
- this does not imply any direct ancestor-descendant connection between humans and elephants, but it shows a homology of bone structure shared by all mammals with four limbs
What indicates transitions between terrestrial amphibious and aquatic forms?
a phylogeny of fossils
what does vestigial mean?
- reduced functions
What did Cetaceans (whales and relatives) have before that they don’t anymore, and what are some evidences?
- used to have 4 limbs, had 2 hindlimbs
- were “walking” whales
- phylogeny of fossil cetacenas
- vestigial hip and limb bones are found in some living and fossil adult whales and in dolphin embryos
- embryology: hindlimbs in cetaceans begin to form but do not fully develop (dolphin embryos)
*** the genetic information to make hind limbs is present, but has been stopped at some point (gene regulation!!!!)
What are 3 examples of vestigial structures on humans?
- tailbone: monkey’s used their tail for balance and locomotion
- goose bumps: chimps erected their hair for emotional display and insultation
- impacted “wisdom teeth” or third molars
What are fossils key evidence for?
- key evidence for the presence, in the geological record (sedimentary rocks), of transitional forms like Archaeopteryx and extinctions of most fossil species
What is the Daphne Major?
- dry volcanic island with cactus & sparse plant cover
When they measured or observed birds, what was the process? (4 things)
- capture
- measure
- collect data
- release
how did the population of finches change from 1976 to 1978?
- 88% died after the drought
- their beak depth increased from 9.4mm to 10.1 mm
What does directional selection change?
- changes the average value of a trait (graph could shift to the left or right - the average decreases to increases)
What is stabilizing selection?
- any selective force or forces which push a population toward the average, or median trait
- average (mean) individuals are favoured, high fitness = stability
- selection against extreme traits
- a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value
- reduction in variation
- When stabilizing selection acts on normally distributed traits, individuals with extreme phenotypes have poor reproductive success
ex. very small and very large babies are the most likely to die, leaving a narrower distribution of birth weights
