EVOLUTION Flashcards
What were the 5 major mass extinctions?
- Cretaceous
- Triassic
- Permian
- Devonia
- Ordovician
What was the biggest mass extinction?
The Permian Period - around 280 mya
What evidence is there that the Permian period occurred?
- fossils in rocks
- 100s of different species below layer while only dozens above
What were the 3 catastrophic events that lead to the mass extinction in the Permian period?
- largest volcanic eruption in Siberia - released CO2 which inc. temps
- methane hydrate melted, released methane, warmed faster and more methane
- methane reacts with O2, dec. in O2, plants die, even more dec, in O2
Types of Adaptations
- adaptations help an organism survive and reproduce in a particular environment
1. Structural
2. Behavioural
3. Physiological
What is a Structural Adaptation?
physical features that change ie body parts, colour, pattern, etc
What is a Behavioural Adaptation?
changes in the way an animal acts
- Inherited - Migration, mating and defenses
- Learned - Communication, making shelter, finding food
What is a Physiological Adaptation?
changes in the metabiome and activity of organisms
ie - Hibernation
What is a Mimicry?
a structural adaptation where a harmless species resembles the look of a harmful species in colouration or structure
ie - Scarlet Kingsnake (harmless) and Eastern Coral snake (harmful)
What is a variation?
Differences between individuals which may be structural, functional or physiological
- not all variations become adaptations
- can be positive, negative or have no effect
What 3 ways do genetic variations come from?
- combination of different gametes (sexual reproduction)
- mutations
- mutations in gametes may be passed on as a new allele NOT somatic cells
What is a mutation
a permanent change in the genetic material of an organism
- the only source of a new genetic variation
What is Selective Advantage?
a genetic advantage that improves an organisms chance of survival in a changing enviornment
What is Natural selection?
- a process where the characteristics of a population change over many generations as organisms survive and reproduce - passing their traits to their offspring
- a result of selective pressures in environments
What is Artificial Selection/Selective breeding?
selective pressure exerted by humans on populations in order to modify or improve particular desirable traits
What is Fitness?
the ability of an organism to survive and reproduce in its environment
- the higher degree means its more likely to survive and reproduce
What is Selective Pressure?
environmental conditions that select for certain characteristics and against others
- Biotic: predators, parasites and competition for food
- Abiotic: heat, water, etc
What are the pros and cons to breeding food crops?
Pros:
- inc. nutritional value
- inc. harvest yeild
- drought and/or pest resistant
Cons:
- may not tolerate soil conditions
- dec. variation
John Ray (1627-1705)
-first scientist to carry out empirical studies on the natural world
- created a classification system for plants and animals based on anatomy and physiology
George-Louis Leclerc
- one of first to publicly challenge the idea that life forms are unchanging
- noted similiarites between humans and apes, theorizing they may share a common ancestor
George Cuvier (1769-1832)
-created with developing Paleontology
-discovered that each stratum (layer of rock) is characterized by a unique group of fossil species and the deeper you go the more dissimilar they get to modern-day
-proposed Catastrophism
What is Catastrophism?
the theory that catastrophes periodically destroyed species living in a particular region, allowing species from neighbouring regions to repopulate the area
Charles Lyell (1791-1875)
- rejected catastrophism and proposed uniformitarianism
What is Uniformitarianism?
-geographical processes happen at the same rates they do today
ie forces that build and erode mountains are no different now then in the past
- slow subtle processes happen over a long period of time that result in substantial changes
Lamarck
-proposed that evolution resulted from inheritance of acquired characteristics
- organisms would become progressively better, inc. in complexity until perfect
What were Darwin’s 5 observations?
- Flora & Fauna: different regions were distinct from different continents ex. rats in South America were similar to another but diff. in Europe
- Fossils: fossils of extinct creatures looked similar to living animals ex. armadillo and glyptodent
- Species resemble each other: finches and other animals on the Galapagos Islands closely resembled those on the west coast of South America
- Diversity: Galapagos species such as tortoises and finches looked identical at first but varied slightly on islands in size and shapes of beaks
- Artificial Selection: traits could be passed down from parent to offspring, sexual reproduction resulted in variation in species
Alfred Wallace
Naturalist that came to similar conclusions as Darwin that natural selection could explain the origin of species, biological diversity and similarities in life forms
What is the Wallace line?
a line between the Malay Archipelago islands between Australia and mainland Asia
- Austalia (West) - mammals with pouches (marsupials) ie kangaroos
- Asia (East) - mammals with placenta ie monkeys
- shows a gene flow as animals migrated from Australia and Asia
- shows evolution and natural selection of animals adapting to their environments
Thomas Malthus
proposed that populations produced more offspring than their environment could support
- inspired darwin and wallace for natural selection and survival of the fittest
What were Darwins 4 main ideas?
- Organisms produce more offspring than can survive, organisms must compete for limited resources
- Individuals of a population vary extensively, and much of this is heritable
- Individuals better suited to local conditions survive to produce more offspring
- Processes for change are slow and gradual
What are the 5 types of evidence that support the theory of evolution?
- Fossils
- Comparative Anatomy
- Comparative Biogeography
- Comparative Embryology
- Comparative Biochemistry
Evidence from Fossils
- older fossils are found in deeper layers and younger are more closer to the surface
- Younger fossils are much more similar to fossils today
- Transitional Fossils - an individual fossil that shares characteristics from two different groups
Comparative Biogeography
- geographically separate locations have different species
- animals found on islands often closely resemble animals found on the closest continent
- this suggests that animals on islands have evolved from mainland migrants
- Fossils of the same species can be found on the coastline of neighbouring continents
Comparative Anatomy
Homologus structures - structures share similar functions due to inheritance from common ancestors ex humans, whales and cats all share phalanges, radius and humorous
Analogus structures - structures share similar functions due to similar environments despite not having common ancestors ex bats and insects have wings for flying but bats are flesh and bones while insects are veins and thin memebrane
Comparative Biochemistry
- all living organisms use the same basic molecules such as DNA and ATP
- the degree of similarity between DNA base sequences and amino acid sequences in two organisms is thought to indicate their degree of relatedness
- Human chromosome #2 is a mutation of 2 chimpanzee chromosomes where the centromere and telomere are connected
What is a population?
A group of individuals belonging to the same species
What is a gene pool?
total collection of genes in a population at any one time
- made of all the alleles of each individual in a population
What is Microeveolution?
a change in a population’s gene pool over a succession or generations
What are the 5 mechanisms of Microeveolution?
- Mutations
- Gene flow
- Non-random mating
- Genetic drift
- Natural selection
Mutations
-change in organisms DNA that creates a new allele that can potentially affect the entire gene pool
ex. poison resistance in Norwegian rats allowed them to survive, able to pass on this selective advantage and inc. poison resistance rat pops. in Europe
Gene Flow
- the net movement of alleles from one population to another due to the migration of individuals
ex. Gray wolves have large territories, one travels over 800km for new territory or breeding partner, when mating they bring all new alleles into a gene pool, inc. diversity
Non-random mating
- selection of mates other than by chance
Non- random mating - preferred phenotype
-chooses mates based on physical and behavioural traits
ex. male caribou fight for mates by using big strong antlers, prevents losing caribou for mating and passing on genes
Non-random mating - inbreeding
closely related individuals breed together, does not affect distribution of alleles but inc. risk of deformations and health problems
ex. self-pollinating flowers inc. homozygous genotypes, causing any more harmful recessive allele to be expressed more
Genetic drift
The change in frequencies of alleles due to chance events in breeding population
Genetic drift - Founder effect
change in gene pool when a few individuals start a new isolated population
ex. strong wind brings pregnant fruit fly to previously unpopulated land, diversity in island is limited
Genetic drift - Bottleneck effect
change in gene distribution from a rapid dec. in population size
ex. typhoon in pingelap island left less than 30 survivors, one has a genetic mutation for colour vision that passed on to offspring and inc. possibilty for that disease in the gene pool
Natural Selection
types of natural selection affect frequency of a heritable trait in a population
- Stabilizing Selection
- Directional Selection
- Disruptive Selection
Stabilizing Selection
favours the intermediate phenotypes by removing the extremes
(middle of graph lump)
Directional Selection
favours the phenotypes at one extreme over another
(build up to one hump on the side graph)
Disruptive Selection
favours the extremes or a range of phenotypes rather than intermediates
(double hump on opposite sides graph; think camel)
What is a species?
a population or groups of pops. that can interbreed to reproduce viable offspring
What is Speciation?
formation of a new species from an existing species
Sympatric Speciation
speciation where populations within the same geographical areas diverge and become reproductively isolated
ex. errors in cell division result in polypolidy in many plants
Allopatric Speciation
speciation in which a population is split in two or more groups by a geographical barrier
What are the 5 pre-zygotic (pre-mating) isolating mechanisms?
- Behavioural isolation
- Habitat isolation
- Temporal isolation
- Mechanical isolation
- Gamete isolation
Behavioural Isolation
species specific signal or behaviour prevents interbreeding with closely related species
ex. eastern meadowlark have short whistle songs while wetern meadowlark have long series of flutes so very little mating occurs
Habitat Isolation
two species may live in the same region but diff. habitat so rarely cross
ex. common garter snake and northwest garter snake live in same regions but common snakes live near water and northwest prefer areas such as meadows
Temporal Isolation
species separated by timing barriers but occupy the same habitat
ex. 3 tropical orchid species bloom for a single day but none of the days overlap
Mechanical Isolation
Genitals are different and do not fit together
ex. sage species can only be pollinated in certain ways one with bees that carry pollen on back and the other with pollen on wings, if the wrong pollinator comes, pollination of the sage does not occur
Gamete Isolation
egg and sperm from diff. species will not fuze to form a zygote
ex. pollen grain of one species fail to germinate on the stigma so no fertilization happens
What are the 3 Post-zygotic isolating mechanisms?
barrier that prevents hybrid zygote from developing into viable , fertile individuals
1. Hybrid inviability
2. Hybrid sterility
3. Hybrid breakdown
Hybrid Inviability
genetic incompatibility of species stops a hybrid zygote during development
ex. sheep and goat embryos die in early development
Hybrid Sterility
the hybrid offspring is sterile and cannot reproduce
ex. mule (horse and donkey) is sterile
Hybrid Breakdown
Hybrid is fertile but their next egenration is weak/ sterile
ex. diff. species of hybrid cotton plants seeds die at early development
What is Adaptive Radiation?
diversification of a common ancestral species into a variety of a differently adapted species
ex. finches in the islands of Hawaii have 28 differently adapted species of finch
What is Divergent Evolution?
pattern of evolution in which species that were once similar to an ancestral species diverge and become increasingly distinct
What is Convergent Evolution?
pattern of evolution in which similar traits arise as diff. species have independently adapted to similar environments
What is Gradualism?
a model of evolution that views evolutionary change as slow and steady before and after a divergence
What is Punctuated Equilibrium?
- model of evolution that views evolutionary history as long periods of stasis or equilibrium that are interrupted by periods of divergence
What was Earth’s ancient environment?
- meteorite bombardment - high heat, no seas
- little atmospheric O2
- lightning
- volcanoes releasing CO2, NH3, CH4 and H2
- ultraviolet radiation more intense since no ozone layer
What were the 4 stages of chemical evolution?
- Abiotic synthesis & accumulation of organic monomers (building blocks for macromolecules)
- Joining of monomers and polymers (ex proteins and nucleic acids)
- Formation of protocells - droplets that produce molecules that differed chemically from their surroundings
- Origin of self-replicating molecules
What is Abiogenesis?
Life started from chemical and thermodynamics
- lost city vents and alkaline vents
What are the 5 changes in the hominid skull over the last 7 million years?
- Dec. prognathism as less jaw muscles needed for chewing
- Dec. in size and sharpness of canines since diet changed to less flesh
- Dec. in cresting as skulls are more smooth
- Inc. in Forehead as the cranial capacity inc. due to growing brains
- Dec. in eyebrow ridge
