Chapter Eight: Evolution Flashcards
What is evolution?
Is the change in genes of a population on earth over time
What is microevolution?
Refers to changes in one gene pool of a population over generations
What is macroevolution?
Refers to speciation, the formation of an entirely new species
Relate individuals and populations to evolution
Individuas can never evolve
A population is the smallest group that can evolve
What is a population
Consists of all the members of one species in one place
What does a fossil record show?
The existence of species that are extinct or have evolved into other species
What age do radioactive dating and half life suggest the earth is
4.6 billion years old
What are the oldest fossils?
Prokaryotes
What are transitional fossils?
Fossils that link older extinct fossils to modern species
What are homologous structures?
Having different functions in different species, but same internal structure; suggesting common ancestry
What are analogous structures?
Same function, but different underlying structures; suggesting adaptation to similar environment, but NOT common ancestry
What are vestigial structures?
Small parts of structures that used to fully exist before. They suggest that anatomy of animals has evolved, such as the appendix which is no longer needed as our diets have changed
What is comparative biochemistry?
Organisms that have a common ancestor have common biochemical pathways
What is comparative embryology?
Closely related organisms go through similar embryonic stages because they have a common ancestor
What are 6 evidences of evolution?
1) fossil record
2) comparative anatomy
3) comparative biochemistry
4) comparative embryology
5) molecular biology
6) biogeography
What process do all aerobic organisms use to respire and what polypeptide do they need for that?
They use ETC
They need cytochrome c
Cytochrome c is present in all aerobic organisms but does differ in between species. What causes this?
Comparison of the amino acid sequence
What does the theory of continental drift state?
250 million years ago countries were locked together as a supercontinent called Pangaea, which separated slowly into 7 different continents
How can study of location be useful to study evolution?
Presence of fossils
What was Lamarks theory?
Individual organisms change in response to their environment and inherit acquired characteristics
Explain in detail the essence of Dawins theory of natural selection (4)
- Populations tend to grow exponentially, to overpopulate and exceed their resources. •Overpopulation results in competition and struggle for existence
- In any population there exists variation and unequal ability of individuals to survive and reproduce
- Survival of the fittest! Only the best-fit survive and get to pass on their traits. This results in evolution, advantageous traits accumulate in a population
What is Dawins degree for fitness?
Measured by the ability of an organism to survive and reproduce in its environment
What was the weakest part of Dawins theory? How is it now explained?
Sources of diversity in a population.
Genetics now explain that (variation from crossover, and random line up on metaphase plate, and mutations)
How did the giraffe “get” it’s long neck?
Ancestral giraffes were all short-necked, although the length did vary between individuals. As population and competition increased, the talkers ones had a better chance of survival. Over time only long-necked ones increased and others were eliminated. NO ANIMALS NECK GREW LONGER, THE AVERAGE LENGTH OF THE NECK IN THE POPULATION INCREASED
How did the giraffe “get” it’s long neck?
Ancestral giraffes were all short-necked, although the length did vary between individuals. As population and competition increased, the talkers ones had a better chance of survival. Over time only long-necked ones increased and others were eliminated. NO ANIMALS NECK GREW LONGER, THE AVERAGE LENGTH OF THE NECK IN THE POPULATION INCREASED
Explain industrial melanism and peppered moths
At first, most were white, only some dark. White moths camouflaged with their environment and Dark’s ones were easy prey. But with industrialization soot polluted the environment and made everything black. This meant dark moths were camouflaged and had the selective advantage. With time, dark ones replaced white ones. NO MOTH CHANGED COLOR, THE FREQUENCY FOR THE DARK ALLELE INCREASED
Relate evolution and drugs such as antibiotics
Antibiotics killed susceptible bacteria and the rest were resistant. THE ANTIBIOTIC DID NOT INDUCE MUTATIONS FOR RESISTANCE. The resistant survivors pass on the traits to make a population resistant
Why is AIDS so hard to cure?
The AIDS virus has the ability to rapidly mutate and evolve and become resistant to drugs. Susceptible viruses become deactivated but the survivors create an entire population of resistant viruses.
Why do some vaccines need to be developed yearly?
The viruses evolve rapidly
The type of natural selection, frequency of inherited traits, depends on __
Which phenotypes of a population are favoured
What is stabilizing selection?
Eliminates the extremes (they just die) and favors more common intermediate forms
What is disruptive or diversifying selection?
Increasing the no. of extreme types at tge expense of intermediate forms
What is balanced polymorphism?
Results from disruptive selection where in the short term 2 or more phenotypes coexist in a population
Disruptive selection in the long term results in …
The formation of 2 entirely new species
What is directional selection?
With changing environmental conditions, one phenotype replaces another in the gene pool
What are the 3 sources of variation in a population?
- mutation
- genetic drift
- gene flow
What are mutations?
Changes in genetic material and the raw material for evolutionary change
What type of mutation can introduce a new allele into a population?
Single point mutation
What is genetic drift?
Change in the gene pool due to CHANCE
What is the bottleneck effect?
When natural disasters reduce population size nonselectively, resulting in loss of genetic variation. The population becomes smaller and not representative of the original one. Certain alleles may under or over represented compared with the original population
What is the founder effect?
When a small population breaks away from a larger one to colonize a new area, it is most likely not genetically representative of the original one, as rare alleles may be overrepresented (due to breeding in extreme isolation between close communities)
What is gene flow?
Movement of alleles into or out of a population, as a result of migration of fertile individuals or gametes
What is population stability?
A stable, non-evolving population, that is, one in which allele frequency does not change in any course of time
(eg 0.5 allele frequency for a trait, if population is not evolving, after 1000 years it will be 0.5)
What is another phrase for the population stability theorem?
Hardy-Weinberg Equilibrium
What are the 5 Hardy-Weinberg characteristics that must be true for a stable population?
- THE POPULATION MUST BE VERY LARGE
- THE POPULATION MUST BE ISOLATED FROM OTHER POPULATIONS
- THERE MUST BE NO MUTATIONS IN THE POPULATION
- MATING MUST BE RANDOM
- THERE MUST BE NO NATURAL SELECTION
Explain the 1st Hardy-Weinberg characteristic
- THE POPULATION MUST BE VERY LARGE. Because in a small one the smallest change in the gene pool will have a major effect on in allelic frequency. If a large one the small change will be diluted and there will be no change in allelic frequency
Explain the 2nd Hardy-Weinberg characteristic
- THE POPULATION MUST BE ISOLATED FROM OTHER POPULATIONS. There should be no migration of organisms into and out of the gene pool because that would alter the allelic frequencies
Explain the 3rd Hardy-Weinberg characteristic
- THERE MUST BE NO MUTATIONS IN THE POPULATION. A mutation in the gene pool could alter the allelic frequency or introduce a new allele
Explain the 4th Hardy-Weinberg characteristic
- MATING MUST BE RANDOM. If individuals select mates, they will be better fit and have a reproductive advantage and the population will evolve
Explain the 5th Hardy-Weinberg characteristic
- THERE MUST BE NO NATURAL SELECTION. Because it causes changes in relative frequencies of alleles in a gene pool
What is the Hardy-Weinberg equation used for?
To calculate frequency of an allele in a population
What is the Hardy-Weinberg equation
p+q=1
(p^2)+(2pq)+(q^2)=1
Where p is dominant and q is recessive
What do each part of the equation stand for?
p^2=AA homozygous dominant
2pq=Aa hybrid
q^2=aa homozygous recessive
What is a species?
A population whose members have the potential to interbreed in nature and produce fertile offspring
How do fragmentation and isolation foster in formation of new species?
The groups are subjected to selective pressures in their environments. With time the groups would have changed so much that they would not interbreed when reintroduced
What are the 6 isolating factors?
1) geographic isolation
2) polyploidy
3) habitat isolation
4) behavioral isolation
5) temporal isolation
6) reproductive isolation
What is geographic isolation
When a species is separated by a natural barrier
What is polyploidy
A type of mutation caused by errors in meiosis, instead of being haploid/diploid they may be tetrapliod or even larger. Such polyploid organisms cannot breed with nonpolyploid ones
What is habitat isolation
When two species live in the same area but encounter eachother rarely (ie land and water)
What is behavioral isolation
It occurs when animals become isolated due to some change in behavior by one group
What’s temporal isolation
It refers to time, such as as to when different organisms of one species sexually mature and become divided into 2 populations.
(eg summer and winter of growing season)
What is reproductive isolation
Closely related species may not be able to mate because of anatomical incompatibility (eg size)
What is divergent evolution?
When a population becomes isolated and is exposed to selective pressures and evolves
Suggest an evidence of divergent evolution
Homologous structures (different function, same structure)
What is convergent evolution
When unrelated species occupy the same environment and are subjected to similar selective pressures and show similar adaptations
Suggest an evidence of convergent evolution
Analogous structures (same function, different structure)
What is parallel evolution
When 2 related species make similar evolutionary adaptions due to living in similar environments after diverging from a common ancestor
What is coevolution?
The mutual evolutionary sets of adaptations of two interacting species
What is adaptive radiation?
Emergence of numerous species from a single common ancestor introduced to an environment
What is gradualism
A theory of evolution stating organisms descend from a common ancestor gradually over time in a branching fashion, and small changes accumulate to big ones. And that fossils should exists as evidence for every stage of evolution with no missing links. This theory is not accepted as fossil record does not support it
What is punctuated equilibrium?
It is the favoured theory today. It proposes that new species appear suddenly after long periods of no change. Most likely, a new species arises in a different place and expands it’s range, competing and replacing ancestral species that become extinct
Explain how the first cell formed
Intense heat, lightning, UV in the atmosphere provided energy for chemical reactions to produce the first organic cell. And due to the lack of free corrosively reactive molecular oxygen the cells created and persisted
What is the heterotroph hypothesis ?
First cells on earth were anaerobic heterotrophic prokaryotes
How did anaerobic heterotrophs form?
They absorbed molecules from the surrounding primordial soup as nutrients
What is the theory of Endosymbiosis?
Eukaryotic cells with nuclei/chlorplasts/mitochondria/etc evolved from prokaryotic cells, as tiny bacteria took up residence in larger prokaryotic cells and performed important functions for the host cell
What is the Cambrian explosion?
Period of time in which many animals (every major phylum) appeared
What followed after animals appeared?
They moved from oceans to land, filling every available NICHE as competition for Limited resources increased in oceans and evolved the traits necessary to survive in a dry environment
Which characteristics enabled animals to move to land?
- lungs
- skin to keep them from drying out
- limbs to move
- mechanisms for internal fertilization
- shells to protect and keep eggs from drying out
Which characteristics enabled plants to move to land?
- roots that anchor them to soil and absorb water
- supporting cells to enable them to compete for light
- vascular tissue to carry water upward
- waxy cuticle to prevent leaves from dehydration
- seeds, a protective package for embryo and it’s food
Name a few factors leading to extinction
Habitat destruction
Environmental change
Interdependence (one extinction leads to another)
Permian mass extinction
Volcanic eruptions covered large areas with thick lava and emitted CO2, and increased global temperature. Almost wiped out life on earth
Cretaceous mass extinction
A massive asteroid crashed and caused a huge cloud of debris to billow in the atmosphere, blocking sunlight for months. Caused land and marine extinctions including all dinosaurs except birds
Summarise 5 important concepts of evolution
- It’s not always slow (eg bacterial resistance)
- It does not occur at the same rate in all organisms (slower in crabs then humans)
- It doesn’t always make organisms more complex (eg starfish is bilateral in embryo, adult is radial)
- It occurs in populations, not individuals (eg giraffes)
- It is directed by environmental changes (eg streamline to move in the ocean)
