1. Natural selection
1.1. 3 types of natural selection
1.1.1. Stabilizing selection: favours intermediate phenotypes and acts against both extreme phenotypes
1.1.1.1. Ex: plants who are too tall have risk of falling over due to wind, but plants who are too short don't get enough sun, so the selective pressures are in favour of medium plants
1.1.2. Directional selection: favours one extreme phenotype instead of the other
1.1.2.1. Ex: only giraffes with tall necks can get food from trees, short and medium necks cannot
1.1.3. Disruptive selection: favours both extremes and acts against the intermediate
1.1.3.1. Ex: light coloured oysters blend in well with sand, and darks blend in with shadows, but grey ones are always out in the open
1.2. the process of change in the characteristics of a population of organisms over many generations
1.3. Selective pressure: A non-living or living environmental condition can be said to select for certain characteristics in some individuals and select against certain characteristics in others.
1.3.1. Ex: temperature change, change in predation
1.4. Charles Darwin: "father" of evolution and the theory of natural selection (he studied finches on islands and found that their beaks adapted to the food source found on each island
1.5. Evolution by natural selection
1.5.1. Overproduction: each species produces more offspring than survive, because more organisms are born than what the environment can sustain
1.5.2. Variation: each individual has a unique set of inherited traits (more variation in a species = more likely to survive since the environment is always changing)
1.5.3. Competition: individuals compete for limited resources
1.5.4. Selection: The individuals with the best traits/adaptations will survive and have the opportunity to pass on it’s traits to offspring.
2. Theories of evolution
2.1. Charles Lyell - Uniformitarianism
2.1.1. Slow, subtle geological processes happen over long periods of time. He believed the Earth's crust was gradually shaped by geological processes
2.1.2. Limitations of theory: Does not take into account varying factors like natural disasters, climate change or impact of human activity
2.2. Charles Darwin - Evolution + natural selection
2.2.1. Theory of natural selection: selective pressures determine which organisms survive (survival of the fittest)
2.2.2. Variation exists within species, and organisms with traits that are better suited will survive, reproduce, and pass on those traits to offspring
2.2.3. Descent with modification: these changes don't demonstrate progress
2.3. Georges Cuvier - Catastrophism
2.3.1. Developed palaeontology, the study of fossils and that each layer of rock had fossils of a different species
2.3.2. Theory of catastrophism states that natural disasters like floods and volcanic eruptions killed species living in a region and allows species from neighbouring areas to repopulate the area, resulting in change
2.3.3. Limitations of theory: does not take into account slow and subtle changes that can occur within a population
2.4. Jean Baptiste-Lamarck - Inheritance of acquired traits
2.4.1. Theory states that species increase in complexity overtime until they reach perfection. Organisms increasingly adapt better, and these traits can be passed onto offspring. Body parts that are unused will be lost overtime
2.4.2. Limitations of theory: Doesn’t reflect how we inherit traits and traits can't be gained just because they would be useful
2.5. Thomas Malthus - Population and carrying capacity
2.5.1. Human populations grow exponentially but food source grows linearly. Overtime, this results in insufficient food sources available (famine, catastrophe, will wipe out human kind)
2.5.2. Carrying capacity is the sustainable balance between population and environment. Populations are limited by food, shelter, water, predators, etc
2.6. Stephen Jay Gould & Niles Eldredge - Punctuated equilibrium
2.6.1. Theory states that evolution occurs both gradually and in small punctuated events
2.6.1.1. During long periods, change is slow, but events such as volcanic eruptions or floods can put huge selective pressures on a population, causing them to change rapidly in a short period of time
3. Artificial selection
3.1. a selective pressure exerted by humans on populations in order to improve or modify particular traits
3.1.1. ex: Cats bred for appearance
3.2. Considered a form of biotechnology because it uses organisms to produce useful products
3.3. Similarities to natural selection: both cause favourable trait to be reproduced and cause allele frequency change
3.4. Differences than natural selection: favourable trait is selected by humans to reproduce not by nature
3.5. Negative impacts: removes variation in a population, reduced gene pool, selectively bred organisms can be more vulnerable to diseases or changes in the environment
4. Evidence for evolution
4.1. Fossil records
4.1.1. Fossils appear in chronological order in the rock layers (rocks closer to the surface are more similar to the species we have today)
4.2. Anatomy
4.2.1. Homologous structures: species with similar structural elements (same set of bones) but different functions Ex: forelimbs in animals have similar structure but are used for flying in bats, running in horses and swimming in whales
4.2.2. Vestigial structures: those that have lost their function but exist because they used to have a function in a common ancestor Ex: Kiwi bird has wings but cannot fly
4.3. Biogeography
4.3.1. The study of organism distribution throughout the world (organisms that live closely together are more similar than those who live farther but in similar habitats)
4.3.2. Ex: Cacti are only found in America even though there are deserts in Africa
4.4. Embryology
4.4.1. Study of the early pre-birth stages of an organism’s development
4.4.2. Ex: all vertebrates have similar stages of embryo development because they all have a common ancestor
4.5. DNA
4.5.1. Ex: humans and chimpanzees have more similar DNA than humans and dogs, so they must have had a common ancestor since DNA is passed on through offspring
5. Origins of life on Earth
5.1. 24 hour timeline for how life appeared on Earth
5.1.1. 12-5 AM: Heavy bombardment period - Catastrophic beginning with lots of collisions - No oceans - Atmosphere filled with CO2 and H2S - First Life Forms: Various types of archaebacteria such as acidophiles, methanogens and halophiles
5.1.2. 5 AM - 1 PM - Life moved to the surface - New bacteria survived and passed onto their offspring
5.1.3. 1-9 PM - Oxygen levels rose from less than 1% to 21% - The increase in oxygen concentration formed the ozone layer - Increase in oxygen concentration allowed for more complex life forms to thrive (cellular respiration)
5.1.4. 9-11:59 PM - First multicellular life appeared on Earth (fish, birds, insects, reptiles, and humans in the last 30 seconds)
6. Adaptation and variation
6.1. Variations within a species: the structural, functional, or physiological differences between individuals within a species
6.1.1. These changes are a result of random mutations and interaction with the environment will determine wether it i positive or negative for an organism
6.2. Adaptation: Adaptations can be behavioural, structural or physiological, and it gives some organisms a better chance of survival and allows those organisms to reproduce and pass on their adaptations.
6.2.1. Result of gradual accumulative changes in a species
6.2.2. Structural adaptation: adaptation in physical features. Ex: Camouflage
6.2.2.1. Mimicry: type of structural adaptation where harmless species physically resemble a harmful species to protect themselves
6.2.3. Physiological adaptation: adaptations that occur within the body Ex: hibernation (allows organisms to survive harsh conditions)
6.2.4. Behavioural adaptation: adaptations in how an organism behave Ex: migrating birds in the winter
7. Microevolution
7.1. Changes in gene (allele) frequencies and phenotypic traits within a population over a relatively short period of time. If these changes are sustained over many generations, it becomes macroevolution
7.2. Factors that contribute to microevolution: mutations gene flow genetic drift non-random mating natural selection
7.2.1. Mutations: changes that occur in the DNA of an individual
7.2.1.1. They introduce new alleles into a population, which changes allele frequencies (mutations are the only way that new alleles are introduced into populations)
7.2.2. Gene flow: net movement of alleles from one population to another as a result of migration
7.2.3. Genetic drift: change in frequencies of alleles due to chance events in a breeding population
7.2.3.1. Founder effect: change in a gene pool that occurs when a few individuals start a new isolated population. This new population is formed by the "founders" who carry some alleles from the original population
7.2.3.2. Bottleneck effect: changes in gene distribution that result from a rapid decrease in the population size. For example, a natural disaster quickly reduces population size, and since the survivors have only a fraction of the original population alleles, the gene pool has lost diversity
7.2.4. Non-random mating: the mating among individuals on the basis of mate selection for a particular phenotype or due to inbreeding
7.2.4.1. Increases amount of homozygous organisms in a population
7.2.4.2. Inbreeding: occurs when closely related individuals breed together (they share similar genotypes, leading to increases in frequency of homozygous genotypes, leading to harmful recessive alleles being more likely to be expressed)
7.2.4.3. Sexual selection: natural selection of mating based on male competition and female preference (males and females have drastically different characteristics)
8. Speciation
8.1. The formation of new species
8.1.1. Allopatric speciation: gene flow is interrupted when a population is subdivided into different geographical areas
8.1.2. Parapatric speciation: part of a population enters a new habitat
8.1.3. Sympatric speciation: occurs when a population lives in the same geographical area but become reproductively isolated
8.2. Species: groups of populations whose members have the potential to interbreed and produce viable offspring
8.3. Macroevolution: Major evolutionary change. The evolution of whole taxonomic groups over long periods of time.
8.3.1. Reproductive isolating mechanisms: in order for one population to become different than another, they must be unable to exchange aleles
8.3.1.1. Post-zygotic barriers: occur after zygote is formed (birth defects, developmental errors)
8.3.1.1.1. Hybrid inviability: even though the zygote is created, it fails to develop to maturity due to genetic incompatibility
8.3.1.1.2. Hybrid sterility: the zygote is born and healthy but is sterile and unable to reproduce
8.3.1.1.3. Hybrid breakdown: the first generation hybrids are fertile, but when these hybrids mate, offspring of the next generation are sterile or weak
8.3.1.2. Pre-zygotic barriers: block fertilization from happening (prevents successful mating)
8.3.1.2.1. Behavioural isolation: two populations do not exchange alleles because they don't respond to one another's mating rituals
8.3.1.2.2. Temporal isolation: two populations do not exchange alleles because they are only available during different times of the year or day
8.3.1.2.3. Ecological isolation: two populations do not exchange alleles because they are in different geographical locations
8.3.1.2.4. Mechanical isolation: two populations do not exchange alleles because they are anatomically incompatible
8.3.1.2.5. Gametic isolation: two populations exchange sperm and eggs but they rarely fuse to form a zygote
9. Pathways of evolution
9.1. Overtime, evolution can follow many different paths
9.1.1. Divergent: pattern where two species become increasingly different
9.1.1.1. Responsible for having apes as our common ancestor and for the current diversity of life on Earth
9.1.1.2. Adaptive radiation: When divergent evolution occurs in rapid succession, or simultaneously, among a number of populations
9.1.1.2.1. Species “radiate out” from a common ancestor (one original species gives rise to three or more species).
9.1.1.2.2. Result of differing selective pressures or genetic drift. Often happens when two closely related species go into different habitats
9.1.2. Convergent: pattern when two or more species become increasingly similar in phenotype in response to similar selective pressures. They have a different ancestry but start to show similar physical traits due to similar environmental pressures
9.1.2.1. Ex: hyenas are more closely related to cats than dogs but are more similar to dogs
9.1.3. Coevolution
9.1.3.1. cases when two (or more) species reciprocally affect each other’s evolution
9.1.3.1.1. (ex: the evolution of the morphology of a plant may affect the morphology of a herbivore that eats that plant, which may affect the evolution of the plant, which might affect the evolution of the herbivore, etc)