Readings Midterm 1 Flashcards
decent with modification
- theory by Darwin
- organisms evolve over generations
- the main idea is that species change over time and pass down traits from one generation to the next
biological evolution
the process by which populations of organisms change over generations through alterations in their genetic makeup
Mutations
stable changes in the genetic material where a new variant forms and is transmitted from a parent to the offspring (some have no effect, some change development)
The general process of natural selection
When there is variation in a population, one variant is favoured which increases the individual’s survival and reproduction makes them more fit
- this increases their frequency and thus gradual evolution of this population occurs over the next generations
Basic definition of genetic drift
a random process that can change the frequency of an existing variant in the population
Can sexually reproducing organisms and asexually reproducing organisms create offspring?
No, they cannot interbreed with each other
A basic definition of migration
the movement of alleles from one population to another population
- plays a role in making the genetic makeup of a species unique
Biological classification
in the past, the classification was only based on visible structures
now we can classify using genetic material
Nomenclature
Similar species are grouped with the same genus: Homo
the type species is the species: sapiens
:. Homo sapiens (in italics)
Analogous features
Same function, different structure
Birds and bats = are used both for flying but have different wing structures and evolved independently
Homologous features
Same structure, different function
- share a common origin
- whale flippers and human arms = the same bone structure but one is used for grasping and one is used for swimming
Convergent evolution
unrelated species evolve similar traits to adapt to similar environments or ecological niches
Ecological niche
refers to the role or position a species occupies within its environment
- habitat, resource use, behaviour, competition, predation, etc
Embryonic development
shows the descent from common ancestors in the early stages of a zygote and fetus
- mammalian development resembles developing gill slits like fishes
Examples of vestigial organs
Human Appendix - a reduced piece of the digestive tract (larger in orangutans)
Human Tailbone - prior to when we evolved from tail-animals
Primitive snakes - have been found with almost complete hindlimbs - evolved from lizards that had legs
Vestigial organs
structures that were functional in the past to ancestors that are no longer needed by present-day organisms
How was heredity discovered?
Gregor Mendel - crossing pea plants
True/False?
Asexual species that produce daughter cells without a reduction of chromosomes = signs of being descended from sexual ancestors
True
Bad mutations
if a mutation = bad, it will lower the survival and fitness = eliminated out of population
- if the mutation is affecting a protein and it causes a loss of a function = vestigial genes
*What supports the theory of evolution
Similarities and differences in classification
Homologous/Analogous features
Fossil record
Embryonic development
Vestigial organs
Cells and cellular functions
Hereditary (genetics)
What is geology?
the principle of uniformitarianism and the invention of stratigraphy
Uniformitarianism
James Hutton + Charles Lyell
The present-day Earth’s surface reflects the processes of formation of new rocks by volcanic action + deposition of sediments in rivers, lakes, seas + erosion, wind, winter, ice
- takes many years
- formation of mountains by volcanos + earthquakes + erosions
Principle of stratigraphy
mineral composition and fossils with different layers in rocks (strata)
- Older rocks must lie below the younger ones
- Comparing strata - major divisions of geological time + the rate of the processes
How are fossils made
when an organism dies, the soft parts decay, and the hard/dense parts = make a mould in the sediment
- best fossils = underwater
- due to fossils, Darwin found that humans have evolved in Africa
Cretaceous Era
flowering plants evolved
- ends with the extinction of dinosaurs
- start of oxygen due to photosynthesis
Examples of adaptation
Eyes adapted specifically for aquatic animals
- can see camouflaged prey (transparent animals)
Artificial / Selective Breeding
Breeding 2 species to get a desirable trait/phenotype
- dogs, cauliflower
How has artificial breeding become successful
bc of heritable variation
- over generations, the strains have become different from each other (sexual reproduction, recombination, mutations, etc)
- ALTHOUGH - susceptible to disease
Polymorphism
2 or more phenotypes/genotypes within the species that are controlled by a single gene
- peppered moths = light and dark colours depending on the environment (considered to be morphs or polymorphs of the same species)
Types of heritable variation
- polymorphism
- continuous variation
- heritable variation
Continuous variation
variation in a population where traits show a range of phenotypes
- can be affected by environmental factors
- EX: human height - range of heights in the population (influenced by multiple genes and environmental factors - lack of nutrition may = shorter)
A basic definition of fitness
heritable character differences affecting survival and reproduction
- often favoured due to NS
- The issue with the word fitness = is confusion with the regular everyday term meaning, it is a short-cut term to express the idea that characteristics sometimes affect the chances for organisms to survive or reproduce
An example of NS on humans
used to be selected for strong and large teeth
- now we have dental care, false teeth
- teeth have already decreased a lot in size (may become vestigial)
why are anti-biotic-resistant bacteria so dangerous?
when one bacteria in a population has an allele that is resistant to bacteria, it has an increase in fitness, continuing to reproduce and increasing frequency
- now all the offspring have this resistance
- bacteria reproduce very fast
- anti-biotic doesn’t work anymore
Cancer
- Caused by a mutation that increases the mutation rates of other genes (mutation in the protein that acts as a proof-reading system)
- Cell multiplies with mutated DNA duplicate
- Cancer cells often become resistant to the drugs that try to stop their growth
Problems with artificial breeding
- disrupts normal development, reducing survival and fertility
- often not the more efficient modification versions of themselves because NS cannot control
True/False
Environment favourability has a significant effect on the species in that instance where it is disturbed
True
If the environment = human disturbance = decline in species population = extinction
Darwin’s Finches
same species in different geographic areas that make the finches look different
- different beak shapes = depending on the size and hardness of sizes that they eat
- Galapagos islands = lots of drought and the large seeds were only produced - those with big beaks were favoured (and vice versa)
Advantages and disadvantages of sickle cell anemia
ADV: heterozygous people have a higher resistance to malaria
DIS: usually fatal in the absence of medical treatment
- malformed and clogged tiny blood vessels
Stabilizing selection
- parents leave offspring with most common genes
- when the environment has remained fairly constant
- variation between the 2 extremes that NS selects for
- EX: human birth weight - low weight and high weight = die
- intermediate weight = best survival
sexual selection
males to obtain mates - succeed in courtship or contests with other males = offspring with females
- females = picky (depending on courtship, scent, songs)
EX: peacocks = long tails = favoured by females
- Long tails = inconvenient for fighting but are still selected for due to sexual selection
Interbreeding
- breeding within a species in a different population (intraspecific interbreeding)
- breeding between different species (interspecific interbreeding)
- INCREASES DIVERSITY
Continuum of Forms
Without barriers to interbreeding there would be continuous variation among organisms, and we wouldn’t observe distinct, separate species. Instead, we would see a gradual blending of traits across populations
List the barriers to interbreeding
Prevent Mating:
1. Geographic barriers
2. Mechanical Isolation
3. Behavioural barriers
4. Gametic Isolation
5. Temporal Isolation
After Mating:
6. Hybrid inviability
7. Hybrid sterility
8. Hybrid Breakdown
Geographic Barriers to Interbreeding
- Physical separation - mountains, rivers, oceans, large distances
- prevention of species coming together to mate
- EX: squirrels on opposite sides of the Grand Canyon = evolved into different species
Temporal Isolation
- species breed at different times (seasons, time of the day)
- frogs that breed in the spring, and others that breed in the winter = impossible to breed
Behavioural Isolation
- species that have different mating rituals, courtship, scents, songs, dances, etc
- EX: birds have specific songs to attract females, others may not recognize the potential mates
Mechanical Isolation
- differences between reproductive organs in the body to make a successful fertilization
- Insects = certain shaped genitalia, making it impossible to mate with other species
Gametic Isolation
the sperm of one species may not be able to fertilize the egg of another species due to chemical incompatibilities between gametes
- Marine species release gametes in the water - only sperm from the same species has the chemical ability to fertilize the egg
Hybrid Inviability
- when interbreeding occurs but the hybrid embryo fails, early death, unfinished development
Hybrid Sterility
Hybrids that are born but are sterile and cannot produce their offspring
- EX: Mules - an interbreed of a horse and a donkey but cannot make future generations of mules
Hybrid Breakdown
Hybrids that are successful in the first generation but the second generation is either inviable, or sterile
Migration
when some of the population diverges or stays with the original population
- if they successfully interbreed the genes become homogenized genetic variation
Low mobility (snails) = low migration rates
High mobility (insects, birds) = high migration rates
True/False
Can strong natural selection can make species adapt to environmental extremes?
True
Local adaption can make species adapt to the environment
EX: Plants that grow near mines with metal in the soil = metal tolerance and resistance
These populations thrive in the toxicity, and when toxicity is absent these plants fail = diverged in plants
True/False
Migration-driven variation can cause gradual trait changes depending on geographic pressures
True
when migration occurs the process is gradual and contuines to show its affect throughout generations
- Northern population = shorter ears and limbs = conserve heat = something the southern mammals do not have because they did not adapt to it
Gradual Divergence
Species that fall near the extremes of the distrubion become very divergent to the point where they cannot interbreed with the intermediate population
- when the intermediate population becomes extinct, then the divergent species becomes distinct and a new species
True/False
Sterility of hybrid males hints at reproductive isolation
True
sterility = inability for a hybrid to reproduce
Why do populations diverge ?
- environmental differences (climate, food sources, predators, or competitors)
- galapagos finches
- Genetic drift (alleles in small pops can become more common or disappear causing divergence from the original pop)
- Geographic isolation
True/False
Divergence is NOT a by-product of adaptations to certain environments
False
it is a by-product because environments can put pressure on these species and they may develop different characteristics (divergent evolution)
Convergent Evolution
Different populations or even species that live in similar environments (like deserts or aquatic environments) may independently evolve similar traits (like streamlined bodies in aquatic animals) even if they are geographically distant
- sharks and dolphins evolved bc they both had the environmental pressure of water
Divergent Evolution
If the same species face different environmental pressures, they will likely develop distinct characteristics - unique to the others
- darwins finches = developed different beak shapes bc of the food avaliability on their separate islands
detailed genetic drift explaination
- when there is no advantage of a mutation and it is fluctuating randomly in a pop = controlled by genetic drift
- if the variation = advantagous = NS
True/False
There is no relationship between the external characteristics (phenotype) and the strength of reproductive isolation
TRUE
some species can look very different from each other but still be in the same species (galapagos finches)
- you cannot identify reproductive isolation by the phenotype because they may have adapted to different environments
True/False
Once species stabilize into a stable environment there are little changes
True
True/False
Fossils are an accurate tool to see if a species has sudden evolutionary change
False
- Fossilization is a rare event - there may not be a complete fossil record to compare past and recent fossils to see if there is a sudden change
- fossils can only display morphological change, some evolutionary changes may not be to the phenotype
How do can you tell the relationship of a species using molecular evolution
- DNA sequences = useful esp when there are phenotypic differences but they = the same species
- closely related species = molecular relationships (genetics)
- 2 species with the least amount of AA differences = closest
- chimps = humans
What can a genome sequence do?
genome comparisons = whoel DNA coding = rapid, detailed - provide more phylogenetic relationships
What are some factors that cause random gene frequency fluctuations?
- some parents will not = offspring
- some parents = alot of offspring (only their genes get passed on)
- Genetic drift (small pops)
- Mutations
What does the rate of divergence depend on
- the rate at which new neutral mutations arise
- how often a mutation gets passed to offspring - The rate at which genetic drift leads to the replacement of one version of a gene by another
- Larger populations have more mutations per generation but genetic drift happens slower
- these opposing effects = cancels out
:. mutation rate determines the rate of divergence between species
What is the molecular clock?
Helps estimate the time divergence between species - especially when the fossil record are absent
- Rely on slowly evolving molecules to estimate divergence
How do you calibrate the molecular clock
compare DNA sequences from species with known divergence dates
Describe the evolution of proteins
The amnio acid sequences of protein evolve = slowly than DNA sequences because often become impaired
- Harder to compare species that diverged using proteins
Describe the chronology of the first organisms
- Eubacteria + Archaebacteria = the first 2 large divison in bacteria
- Angiosperm
- Animals diverge later
