evolution Flashcards
what is the early idea of where we came from
Early ideas based on religion and philosophy suggest that Earth and all living things had been created in their present forms and were immutable - unchanged and unchanging
What did George Buffon theorize?
- Earth surface change overtime.
- found similarities between humans & apes
- Speculated earth was 6000y ears old
what did Carl Linnaeus find and who were his views similar to
biological nomenclature and Erasmus Darwin had similar views.
what was Erasmus Darwin theorize?
all life had developed from a single source.
what did Jean-Baptiste Lamarck discover
All species evolve over time
A species evolves in response to its environment and becomes better adapted
Acquired traits are passed on from generation to generation
Ex. Giraffes stretch their necks to reach food in trees and eventually pass that trait down to their offspring.
However, he didn’t believe that a single species could give rise to additional species.
what are fossils most often found?
trapped in sediment
what are micro fossils
have microscopic remains
who was Georges Cuvier
Founder of the field of paleontology (study of fossils)
Proposed that fossilized organisms are extinct (contrary to popular belief).
According to experts today, less than 1% of species in the fossil record are living today.
He discovered that
Each layer of rock held a unique group of fossil species
The oldest and simplest fossils are in the deepest layer compared to those in shallower layers
Suggested that catastrophes killed many species (catastrophism) and that these events corresponded to the boundaries between the fossil layers
who was Charles Lyell
Rejected the Theory of Catastrophism
Proposed the Theory of Uniformitarianism
Geological processes in the past operate at the same rate as they do today
Suggested that a slow and continuous process could result in substantial changes in the long term
what is Theory of Uniformitarianism
Geological changes are slow and gradual and the natural laws and processes have not changed over time
what is the Evidence for Evolution
Fossil Record
Biogeography
Anatomy
Embryology
purpose of Fossil Record
Fossils within the younger layers are most similar to species alive today.
Fossils appear in chronological order within the sedimentary layers.
Not all organisms appear in the fossil record at the same time.
looking for transitional fossils that show an intermediary link between past and present groups of organisms.
what are Vestigial structures
structures that serve no useful function in a living organism.
Example: whales have small hip bones (pelvis and femur), suggesting that these mammals evolved from ancestors that possessed hind legs.
use of transitional fossils
show an intermediary link between past and present groups of organisms.
Vestigial feature in humans
Goosebumps/Raising Hair
ailbones
Appendix
Muscles to move the ears
what is Biogeography
Study of geographical distribution of species
Homologous structures
structures that have similar structural elements and origin.
May have a different function.
They originate from a common ancestor.
Ex. Limbs of human/frog/bat, hair in mammals.
Analogous structures:
Structures that do not have a common evolutionary origin.
Perform similar functions.
Provides evidence for adaptation to suit the environment.
examples of Analogous Structures
Ex. wings of insects, birds and bats. All used for flight, but insects do not come from a common ancestor because there are no bones. Example: Penguins and fish both has fins for swimming.
The fin evolved as a structural adaptation, not from a common ancestor
what is Embryology
the study of pre-birth stages of an organism’s development
what is Mutation →
a permanent change in the genetic material of an organism and is the only source of new genetic variation & new alleles being introduced
Mutations can be….
Neutral: no immediate effect on an individual’s fitness, or reproductive success.
Harmful: lowers fitness and the cell no longer able to produce properly functioning proteins and/or chromosomes
Example: serious genetic disorders such as Cystic Fibrosis, Huntington’s Disease
Beneficial: cell gains ability to produce a new or improved protein/chromosomes, giving the individual a selective advantage & increased reproductive success.
Example 1: Sickle-cell allele = resistance to malaria
Artificial Selection
a selective pressure exerted by humans on populations to improve/modify particular traits for future generations.
occurs in captivity rather then in a natural setting
Examples: cats/dogs breeding, cows bred for more muscle for meat, chickens bred to produce more eggs.
Advantages of selectively breed crops:
To increase nutritional value
To increase the production at harvest (economy)
To be drought-resistant or pest-resistant (allowing seasonal harvest)
Produces dramatic changes in traits of a population (i.e. chihuahuas vs wolves; wild strawberries vs Large store strawberries)
Reduces genetic diversity within a population (loss of biodiversity)
Monoculture: planting the same varieties of a species over large expanses of land.
Disease = most crop infected
explain Darwin’s Theory of Evolution
Used his observations to propose the “Theory of Natural Selection” - the way in which nature favours the reproductive success of some individuals within a population over others
life has changed and continues to change, due to natural pressures
what did darwin observe
Flora and fauna of the different regions were distinct from those in Europe.
Example: rodents in South America were structurally similar to one another, but different from other continents
ossils of extinct animals looked very similar to living animals
Example: extinct glyptodon and modern armadillo from South America
Finches and other animals Darwin saw on the Galapagos Islands
closely resembled animals he had observed on the west coast of South America
summarize Theory of Natural Selection
Organisms produce more offspring than can survive (leads to competition for resources between members of the same species)
Individuals of a population vary extensively (comes from inheritable traits)
Individuals better suited to local condition survive to reproduce
Processes for change are slow and gradual
Radiometric Dating
the study of radioactivity provided geologists with the means to estimate the absolute age of Earth with much greater precision.
Every meteorite that has struck Earth has shown to be 4.6 billion years old. Moon rocks were discovered to be 4.53 billion years old.
Scientists believe that the Earth has been around for 4.6 billion years.
Radioisotopes
atoms that undergo radioactive decay, and radioactive decay rates can be measured very accurately. Radioactive decay changes a parent isotope into a daughter isotope of the same element or different element.
Each radioisotope decays at its own constant rate, measured in a unit called a half-life
This is the time it takes 50% of a sample parent isotope to decay into a daughter isotope.
Directional Selection
Favours phenotypes at one extreme over the other.
Common in artificial breeding
Common during environmental change
Example: Peppered moth
Stabilizing Selection
Favours intermediate phenotypes and acts against extreme variants of the phenotype
Reduces variation
Example: Birth weight in humans
Disruptive Selection
Favours the extremes of a range of phenotypes rather than intermediate are favoured
Intermediate phenotypes can be eliminated
Environmental conditions may favour more than one phenotype.
ex: 2 species of plants with different-sized flowers may be available as a hummingbird food source. There may not be any intermediate-length flowers, just small and large.
Sexual Selection
Favours the selection of any trait that influences the mating success of the individual
Combat (caribou)
Visual display (Peacocks)
Traits favoured in sexual selection include sexual dimorphism (striking differences in the physical appearance of males and females).
The most common forms of sexual selection result from female mate choice and male vs male competition
Directional Selection
favours extreme phenotypes (i.e. cross-breeding)
Stabilizing Selection
favours intermediate phenotypes (“average;” reduces variation)
Disruptive Selection
favours both extreme phenotypes (eliminates intermediate phenotype)
Sexual Selection
Favours the selection of any trait that influences the mating success of the individual (female mate choice and male vs male competition)
Evolutionary Change
Individuals organisms do not evolve populations do
Therefore when we study evolutionary processes we study the changes in population
Under a set of specific conditions, a given gene pool (total of all alleles within a population) remains unchanged from generation to generation.
5 key factors that can cause evolution, a change to the gene pool of a large population or a species.
Natural selection: favours the passing on of some alleles over others
Small population size: increases the likelihood of genetic drift
Mutation: introduces new alleles to a population
Immigration or emigration: introduces or removes alleles in a population
Nonrandom mating: preferred mates will pass on their alleles more often
what is a Genetic Drift
A change in the genetic makeup of a population resulting from chance in small populations
Smaller populations = GREATER genetic drift and less likely it is that the parent gene pool will be reflected in the next generation
Any lost alleles result in a net reduction of diversity of a population
what are the Two situations that can lead to significant genetic drift in large populations
Bottleneck Effect
A dramatic, often temporary, reduction in a population size usually resulting in significant genetic drift.
Disease, starvation, overhunting, natural catastrophe
Only a very small sample of alleles survives to establish a new population
Loss of genetic diversity
Founder Effect A small number of individuals separate from their original population and find a new population Reduces genetic variation/gene pool Common in islands New “founders” carry some but not all of the alleles from the original population’s gene pool.
macroevolution
The same selective mechanisms found in natural selection are able to account for Speciation - the formation of an entirely new species.
microevolution
Evolutionary changes that occur at the species level are referred to as
what are the Two types of reproductive isolating mechanisms
Pre-Zygotic
Post-Zygotic
Pre-Zygotic Isolating Mechanism
Temporal Isolation
Reproductive cycle for flowering or mating occur at different times, even though in the same area.
Very common in flower species.
Behavioural isolation: Species have a specific signal or behaviour that prevents closely related species from interbreeding.
Mechanical isolation
Structural differences in reproductive organs can prevent copulation.
Ex: The genital in insects operate like a lock & key model
Gametic isolation
Sperm and eggs of the same species only recognize each other by molecular markers.
In other cases, the male gamete cannot survive inside the female.
whata re the 3 post-zygotic mechanisms
Zygotic mortality
- No fertilized zygotes or embryos develop to maturity
E.g. hybrid embryo between sheep and goats die before birth
Hybrid mortality
- Hybrid offspring are unlikely to live long.
Offspring are weak and sterile.
Hybrid Sterility
- Offspring of genetically dissimilar parents are likely to be strong but sterile.
Meiosis fails to produce normal gametes in the hybrid offspring.
Example: horse + donkey = mule
Mules = sterile
Allopatric Speciation
Populations are separated by a geographical barrier and diverge genetically.
Gene flow is interrupted
Separation can occur due to river, water level change, geological remodelling etc
Ex. birds being able to cross large expanses of water versus those that don’t
Sympatric Speciation
Populations in same geographical area become reproductively isolated
More common in plants than animals
New species evolves within a large population
For example, a new mutation immediately results in reproductive isolation, but not ecological isolation.
Human Influence on Speciation
Separation of populations can also threaten the survival of species. Many human activities (agricultural expansion and roads) cause fragmentation of habitats, that effectively isolate populations.
→ Conservation Efforts to maintain gene flow are now considered. For example, Wildlife corridors connecting strips of forests
Adaptive Radiation
Type of allopatric speciation
Rapid evolution of a single species evolves into a number of distinct but closely related species, filling a variety of formerly empty ecological niches
New resources that were not being used by other species become available
Little to no competition
Divergent Evolution
2 or more species with the same ancestors, evolve increasingly different traits, resulting from differing selective pressures or genetic drift.
Convergent Evolution
Similar traits arise b/c different species have independently adapted to similar environmental conditions.
Example: sharks and dolphins (streamlined bodies).
Example 2: Birds and bats (wings).
Both examples don’t have a common ancestor
Coevolution
1 species evolves in response to the evolution of another species
2 species become completely dependent on one another for survival, and their evolutionary pathways become linked.
Common among flowering plants and pollinators
Theory of Gradualism
As new species evolve, they appear similar to the original species and gradually become more distinctive
Theory of Punctuated Equilibrium
Process of evolution is slow, but occasionally there are spurts of rapid change
Theory of Punctuated Equilibrium
Three assertions
New species evolve rapidly over time
Speciation usually occurs in small isolated populations and leaves behind few transitional fossils
After the initial burst, additional changes are very slow
