Chapter 15 Flashcards
evolution general definition
change within organisms over time, 2 types:
development
acclimation: response to changing environment conditions
specific (biological) definition
change in the genetic makeup of a population over time
according to this definition, populations evolve, individuals dont
pre darwin ideas (aristotle)
species dont change over time
natural order exists in the world and does not change
plato
all objects can be represented by ideal forms
variation between indivduals represents a deviation from the ideal form (so is not important)
jean lamarack
2 driving forces in evolution
1. linear force:
evolution towards increased complexity and perfection
this is driven by some internal force in all living things
2. lateral force: adaptation to local conditions
organisms have features that suit them to where and how they live
mechanims for adaptation is use an disuse of parts:
body part that develop in a certian way during an individual life are passed to its offspring
charles darwin
sailed around the world in the 1830s as a naturlist on the beagle
proposed a mechisms for evultion in 1830s
continued to develop collect evidence for evolution for 20 years
1858:
alfred wallace devlopment the same idea as darwin
the origin of species
published in 1859
darwin was influenced by two ideas
- uniformitarianism: world is under constant slow change
large changes can occur over long periods of time
essay on population (1798, thomas malthus)
human population grow faster than resource supplies
when populations are stable, individuals suffer fro lack or resources
darwins mechanims for evolution: theory of natural selection
observations:
1. all organisms can reproduce at an exponential rate
2. populations do not increase expontially
3. resources are limited
the ideas of malthus apply to natural population
conclusion 1:
there is a struggle for existence between organisms within a species
observations:
4. indivduals in populations vary in a number of traits
5. some varibility is inheritied
conclusion 2:
the ability to survive is related to variation in different traits
indivduals with traits that allow them to survive in particular situations pass these traits to their offpsring
conclusion 3:
over many generations populations evolve, adapting to their enviorment
populations of the same species, in different environments, will evolve into different species
conclusion 4:
applying the concept of uniformitarnisam:
all species have evolved from a common anscestral species
theory does not explain were new variation comes from
impact of darwins ideas
branching pattern of evolution- all living things envolved from a common ansestor
non-constancy of species
struggle for existance is dominant force in nature
importance of variation within species
importance of probability
random events:
1. new variation
2. presence of organism in particular enviornment
the success of an orgainsm is partly a random event
evidence for evolution
artifical selection: organisms can be bred to look different
biogeography
because they share a common ancestor, organisms from one region are more similar to each toher tha organisms from other regions
fossil record
fossils are not arranged at random
fossils of recent origin, in a region resemble organisms living in the region
groups of organisms are found in similar aged rock layers in different places
comparative anatomy
related organisms are built from the same basic parts
homologous structure: body parts similar in structure but can be functionally different ex) from a common ansestor
analogous stucture: body parts different in their basic in structure but functionally similar (from different anstror
vestigial (non fucntional) organs
organisms retain body parts of ansestors even when they are not used
molecular biology
evolutionary reltionships can be implied from the chemical or genetic simsilarity if organisms
co evolution
organisms that rely on one another show similar evolutionary patterns
ex) lice on mammals
traditional agruements against evolution
there have been disagreements about:
the fact of evolution
the mechanism of evolution
does eolution occur by natrual selction
lack of what in fossil record
intermediate forms
dilution of favourable traits ex ) tall plants
each generation of offspring fo the tall plant becomes shorter since it crosses with short plants
evolution works this way if inheritance is blending
but inheritance is particuulate
so, the tall trait does not become diluted
blind watchmaker
- mutation is a random process
- complex structures require many mutations
3 it is highly (impossible for random mutations to create complex sturctures
however: the evolution of complex stuctures is possible if intermediate structures are preserved
irreducible complexity
incomplete stcutures are not useful and complete stcutures are too complex to evolve in a single step
however, some incomplete stcuture can be useful as they envolve they may change their function
sea vents
chlorophyll liek pigemtns may have evolved to detect photons from deep sea vents
bacteria need to be close to vents
photons coming from vents are too weak for photosynthesis
different types of natural selection
selection can be classified by the traits that increase fitness
for a continuous trait we expect a distrubtuion like this: moutian curve
1. stabilizing selection
2. directional selection
3. disruptive selection
4. frequncy dependant selection
stabilizing selection
indivduals with average traits are selected
decrease the variation in the population but does not change the avaerage value of a trait
probably occurs in most populations when the enviornment is stable and organisms are adpated to where they live
directional selection
individuals with higher or lower than everage traits are selected
decreases variation and changes the avaerage value of a trait
occurs when the anvironment changes and organisms adapt these changes
disruptive selection
individuals with higher AND lower than average traits are selected
creates two peaks in the abundance of a trait:
occurs whem resources are unevenly distrucbuted in the enviornment
frequency dependent sleection
individuals with uncommon traits are selected
tends to balance the proportion of individual with different traits
example of frequency dependent selection
diease and parasite resistance: dieases envolve to infect common genotypes
sex ratio: proportion of reproductive male and female tends to be equal
other mechanisms of evolution
mechanisms that do not result in adaptation to the environment
sexual selection
also proposed by darwin
some indivduals have traits which may decrease their ability to survive but increase their access to breeding partners
2 forms of sexual selection
- females show prefernce for males with certian traits
- males compete with one another for access to females
size differneces between males and females may be the result of sexual selection
random selection of indivuduals in small populations
change in the genetic makeup of a population by random events
invloves elimination of genetic info from a population
founder effects
only a few individuals in a pop colonize a new habitat
by chance, these few indivdiuals have different traits compared to the parents population
bottleneck effects
all but few individuals in a population are eliminated
surviving indivdiuals do not contain the same genetic stucture as the orginal population
genetic drift
non adaptive change in a population over time
ex) ABO blood type distribution
ex 2) allele for HIV restistance
some patterns of human genetic are a
mix of adaptive and non adaptive mechanisms of evolution
low pigments increases vit D production
pigmentation provides UV protection
