Evolution and Ecology Review

Thomas Malthus In 1800s, he thought food supply was not going to keep up with rapid population growth. He thought this would lead to disease, starvation, and mass death. Resources would be limited, and there would be a struggle for survival. Darwin realized from reading Malthus that this struggle occurs in populations of all living things, not just humans. ALL populations produce more offspring than can survive, so there is a struggle for survival. Those who have the most fitness survive and reproduce.

Natural selection Organisms with traits best suited to their environment are more likely to survive and reproduce ie bunnies on pHET simulation in class. White bunnies succeed in white arctic environment. Mutated brown bunnies are less successful. If, over many generations of bunnies, the environment warms and snow melts, the mutated brown bunnies will be more successful.

Alfred Wallace Came up with the idea of natural selection at about the same time as Darwin Wallace Darwin

Evidence for Evolution Fossils Vestigial structures DNA similar And more…

Fossils – strata, relative dating

Fossils Preserved remains or traces of organisms long dead. Not alive today but any similarity to us?

Vestigial Structures Structures on organism that have no apparent use. Idea is that they were once useful and are slowly becoming smaller over generations. EX: mole rat eyes, whale hips, snake hips, tailbone, ear muscles, dewclaw (dog thumb), etc…

Selection: Stabilizing, Directional, Disruptive If lightIf lightIf medium and dark and mediumtrees dietrees die

Selection: Stabilizing, Directional, Disruptive Stabilizing: population shifts to middle (intermediate) phenotype Directional: population shifts away from one extreme phenotype toward intermediate and the other extreme phenotype Disruptive: shift to both extreme phenotypes, decrease in intermediate phenotype

Homologous structures /divergance Similar structures that have evolved over time From the same ancestral structure. Can have very different functions, but similarity suggests a shared ancestry /evolutionary relationship.

Analogous Structures/convergence Structures that have similar function but did NOT evolve from the same ancestral structure. Dragonfly wings also analogous to these.

Homologous vs. analogous structures

Founder effect

Hardy Weinberg Formula To determine a shift in allele frequencies within a population (determine if evolution is happening in a population. ) p 2 + 2pq + q 2 = 1 and p + q = 1 p= frequency of DOMINANT brown bunny allele (B)=??% q=frequency of RECESSIVE white bunny allele (b)= ??% p 2 = % of BB genotype (homozygous dominant) q 2 = % of bb genotype (homozygous recessive) 2pq = % of Bb genotype (heterozygous) Count homozygous recessive individuals (bb) and you get q 2. Take square root and you get q, so do 1-q to get p. Now you have BOTH p and q, or the allele frequencies for first generation. Now wait and do the same thing for the second generation to see if there has been a shift in allele frequency.

Sexual vs. Asexual reproduction Sexual involves two parents whereas asexual involves one. In sexual reproduction, the genetic information of the two parents can be combined in nearly infinite ways to produce highly diverse offspring – more diverse than offspring produced by asexual reproduction.

Sexual selection An example of natural selection. EX: female attracted to peacock (male peafowl). The brighter, the higher the male’s fitness and chance of reproductive success.

Carbon 14 dating -radioactive dating

Carbon-14 dating (Radioactive decay)

C 14 half life Every 5730 yrs, ½ of the mass of a sample of carbon-14 decays to nitrogen-14. The percent of carbon 14 is maintained in the environment through ionizing radiation. When you die you stop taking up NEW Carbon 14, and the Carbon 14 you have continues to decay.

Half-life This the the amount of time it takes for ½ the mass of a sample of a radioactive substance to decay In Carbon 14, this time is 5730 yrs.

C 14 half life Because we know how much carbon-14, by mass, should be in a sample of bone at the time of death, we can determine how long ago death occurred based on what fraction of c-14 remains in the bone. If half remains, it has gone through 1 half life (5730 yrs.) If a ¼ remains, then it has gone through 2 half lives (11000 yrs)

Variation in populations Darwin said very important for natural selection Not so much 

Period of recovery and adaptive radiation (after mass extinction or inhabiting new area) an event in which a lineage rapidly diversifies, with the newly formed lineages evolving different adaptations.

Ecology Successional change

Successional change-pioneer species and climax community Build soil where there is none (new volcanic islands)

Climax community (see picture in previous slide) It represents a self-perpetuating, stable assembly of organisms, and undergoes little change over long periods of time. The species assembled together are very complimentary, they do not directly compete for same resource at same time. The degree of their niche overlap is minimized.

Lichen on rock

Niche What’s eating you? What are you eating? Who gets affected if you and your whole population were to disappear?

Carrying capacity maximum number of individuals of a given species that an area's resources can sustain indefinitely without significantly depleting or degrading those resources

Carbon cycle – carbon flow Biological and non-biological reservoirs

Acid rain

Energy flow in ecosystems – not a cycle since not return to sun

Global warming Arctic sea ice and polar bears Less able to hunt due to decreasing ice floes, and which could move too far away from land.

Eutrophication

The process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. These typically promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish. Eutrophication is a natural, slow-aging process for a water body, but human activity greatly speeds up the process.”nutrients

Causes of extinction CausesLink.html CausesLink.html

Species definition 2 organisms are from the same species if they can mate and produce fertile offspring.

Dihybrid crosses Practice them

Increase or decrease in complexity as you dig down?

Why similar? CH 16.2

Mechanisms of Control All cells in an embryo inherit the same genes, but they start using different subsets of those genes during development The orderly, localized expression of master genes gives rise to the body plan of complex multicelled organisms

Population # of individuals in a species that occupy a given region at the same time. ie students at ghchs = 4400