Evolution Flashcards
Evolution
Descent with modification - the idea that species change over time, give rise to new species, and share a common ancestor.
Precambrian Era
- Hadean
- the earth froms from gas
- ocean forms - Archaen
- the first organisms appear - Proterozoic
- first eukaryotes appear
- first multicellular organisms
When did the Earth form?
4.6 BYA
What were the first organisms and when did they form?
Anaerobic prokaryotes - more than 3.5 BYA
Oxygen enters the atmosphere
Released by photosynthetic bacteria 3 BYA
When did the the first eukaryotes form?
About 2 BYA
When did the first multicellular organisms evolve and what were they?
Algae and soft-bodied marine invertibrates - about 1 BYA
Paleozoic Era
570 MYA - 245 MYA
- first vertibrates
Cambrian explosion
Period at the beginning of the Paleozoic Era that saw a fast evolution of life in a short period of time. Most modern groups of animals evolved during this period.
1st Mass Extinction
End of the Paleozoic Era - 245 MYA
96% of marine life
Mesozoic Era
245 MYA - 65 MYA
Age of dinosaurs
2nd Mass Extinction
End of the Mesozoic Era - 65 MYA
Dinosaurs are killed, mammals survive
Crash of a meteorite in the Yucatan Peninsula of Mexico, dust cloud blocks out the sun
Cenozoic Era
65 MYA - 0 (modern)
Age of mammals and humans
Evolution of humans
Quaternary period
500 000 years ago, mordern human
Creationism
the religious belief that nature, and aspects such as the universe, Earth, life, and humans, originated with supernatural acts of devine creation
Aristotle
- naturalist/philosopher
- put all organisms into a ladder scheme - Scala Natura
- each organism on the ladder was permanent and never changing
John Ray
- defined “species”
- classification system for plants and animals based on anatomy and physiology
Carolus Linnaeus
- grouped plants and animals according to structural similarity and divided them into orders
- followed Biblical beliefs (all species were created and do not change)
Georges-Louis Leclerc, Compte de Buffon
- noted similarities between humans and apes
- idea that species change over time
James Hutton
- natural forces are responsible for sculpting the Earth’s surface
- uniformitarianism
Uniformitarianism
The idea that the Earth has always changed in uniform ways through the same processes in the past and present
Jean-Baptiste Lamarck
- recognized that living things changed over time and are descended from other species
- inheritance of acquired traits: licing things can modify their body through use and disuse of parts and then pass them on
George Cuvier
- paleontologist
- theory of catastrophism
Catastrophism
A vast amount of species was originally created; successive catastrophes shaped the Earth, produced layers of rock and created fossils
Thomas Malthus
- human population was reproducing at a rate that would lead to lack of food, then, there would be a struggle for existence (starvation, war, disease)
Charles Lyell
- refined Hudson’s ideas on unifromitarianism to include slow change over long periods of time
- “Principles of Geology”
- fossils are a concrete record
Alfred Wallace
- theory of evolution through natural selection (with Darwin)
Species observed in different ecosystems that are close geographically are more similar than species in similar ecosystems far away.
Common ancestor, sperated by georaphy
Fossils of extinct animlas are very similar to present animals in the same regions
Organisms evolve, the descendants of a species can be modified
Species on the Galapagos Islands closely resembled species on the nearest coast
Common ancestor, sperated by georaphy
Species of animals that at first looked identical actually varied slightly from island to island
Adaptive radiation
Adaptive radiation
Had a common ancestor, then differenciated into separate populations/species, each adapted to the local environment
Read “Principles of Geology”
Environment acts as a selective pressure
Selective pressure
an evolutionary force that causes a particular trait to be more favourable in certain conditions
Darwin’s Theory
- Variations exist among individual species
- Individuals compete for resources
- Competition leads to death of some, survival of others
- Individuals that have advantageous variations (adaptations) are more likely to survive and reproduce
Adaptation
A particular trait (structure, physiology, or behaviour) that helps an organism survive and reproduce in a particular environment
Macroevolution
Evolution on a large scale. Result of a new species from a common ancestor or evolution of one species into two
Microevolution
Evolution on a small scale. Changes in allele frequencies of a gene within a population over time. Evolution within a species due to adaptation
Natural Selection
A process whereby the characteristics of a population of organisms change because individuals with certain variations of inheritable characteristics are better equipped to survive specific local environmental conditions and pass on their traits to offspring
Fitness
a measure of an individual’s ability to survive and reproduce
Variations
Arise due to genetic drift, gene flow, and mutations. give certain individuals advantages over others
The Fossil Record (Paleontology)
The most direct evidence of the history of life on Earth.
Appear in chronological order. Recent fossils are more similar to modern organisms.
Organisms do not appear simultaneously in the record.
Transitional fossils - organisms evolved slowly
Fossils
Preserved remains, or imprints of remains, of ancient organisms.
Created when organisms are buried in sediment; hard materials are mineralized.
Transitional Fossils
Fossils that exhibit traits common to both an ancestral group and its derived descendant group. Ex. Archaeopteryx
Biogeography
The study of the geographical distribution of species.
Animals on islands have evolved from land migrants, adapting to the environment.
Geographically close regions are more similar than ecologically similar ones.
Anatomy
Exhibiting structures that appear to have the been derived from a common ancestor.
All vertibrates share the same pattern of body structures (more complex fish - reptile - mammal)
Homologous Structures
Parts of the body that have the same origin (same underlying structure and common ancestor), but different functions (different environments)
Analogous Structures
Parts of the body that have different origins (different underlying structures, ancestors), but have the same functions (similar environments, evolved separately)
Vestigial Structures
Parts of the body that seem to have no function. Evolutionary baggage
Embryology
Study of embryos. Similar features in embryos of unrelated organisms at different stages suggest common ancestry
Molecular Biology
Evolutionary relationships among species reflected in their DNA and proteins. More similar DNA means more closely related.
Taxon
A grouping of population(s) of organism(s) classified by taxonomists
Phylogeny
A hypothesis about the evolutionary history of groups of organisms
Cladistics
A classification scheme based on phylogeny.
Based on the idea of speciation: groups of related organisms have one common ancestor, from which they retain some traits and gain others as they evolve and diversify
Clade
A group of organisms that includes an ancestor and all of its descendants.
Method of comparing traits to determine ancestor-descendant relationships.
Based on cladistics
Cladogram
A diagram used in cladistics to show relations among organisms.
Illustrates relationships among organisms and evolutionary relationships for organisms with a common ancestor
- the closer, the more closely related
- branching off points: hypothetical ancestor
What is the importance of cladistics?
Closely related species have similar genes. Helpful when looking for medicine, as scientists can look at species that have valuable proteins and chemicals. Helps trace transmission of disease and develop and test possible treatments
The closer the relantionship between species…
The more similar the amino acid sequence
Population genetics
The study of the frequency of alleles and genotypes in a population.
Important to microevolution: changes in genetic variability determine change in the population
Frequency
The number of occurences of a particular allele divided by the total number of alleles in the population.
Changes in allele frequency over time result in evolution
Hardy-Weinberg Equilibrium
When genotype frequencies are constant throughout generations.
Provides a baseline to determine whether or not gene frequencies have changed in a population and thus, whether evolution has occured. (never occurs in nature)
Hardy-Weinberg Principle states:
In the absence of forces that change the allele frequencies at a given locus, the original genotype frequencies will remain constant from generation to generation, in a large population with random mating. The genotypes are said to be in Hardy-Weinberg Equilibrium because the proportions don’t change.
Conditions for Hardy-Weinberg Equilibrium
- Population is large
- Mating is random (no selection for partners/phenotypes/genotypes)
- Isolation - no emmigration/immigration (no exchange of genes)
- No natural selection (certain alleles don’t give a reproductive advantage)
- No mutations
Formulas
p + q = 1
P^2 + 2pq + q^2
Mutation
- permanent changes in the DNA (must be in gametes to be inherited)
- provied new alleles and therefore variation
- if they give a selective advantage, their frequency is increased
- Ex. Daphnia water flee (survives at higher water t)
Genetic Drift
- change in allele frequency caused by chance
a) Bottleneck Effect: population is greatly reduced by events such as natural disasters or overhunting, resulting in certain alleles being under represented and others being over represented. Ex. Northern elephant seals
b) Founder Effect: when a few members of a population colonize a new area, they do not represent all of the alleles in the original population. Ex. Honey creepers (Hawaii)
Gene Flow
- gene migration - addition of an immigrant’s alleles to the gene pool
- Ex. different populations of fish mating
Non-Random Mating
- selecting for specific partners (and alleles)
a) Inbreeding: mating between closely related partners. Increases homozygosity and recessive alleles, which can lead to genetic disease
b) Assortative mating: choosing partners with a similar phenotype
Natural Selection
- advantageous alleles are selected for
a) stabilizing - favouring intermediate
b) directional - favouring one extreme over the other
c) disruptive/diversifying - favouring both extremes
Adaptation
Any trait that enhaces an organisms fitness or increases its chances of survival and probability of successful reproduction.
Arise from a series of small adaptations as populations are subjected to changing environments (the best-suited are selected for)
Genetic fitness
An organism has adaptations/traits that increase its chances of survival and reproduction in a SPECIFIC ENVIRONMENT
Structural (Anatomical/Physical)
- anatomical changes in the shape or arrangment of particular features either internal or external
- Ex: body coverings and parts, MIMICRY (cryptic colouration; appears like another organism), camouflage, homologous/analogous structures
Physiological
- changes in the biochemical functions inside organisms
- Ex: chemical defenses (venom, ink, sprays), silk, anitbiotic resistance
Behavioural
- how organisms respond to their environments
- Ex: migrations, pack hunting, hybernation, plants to light
Exaptation
- the process by which an adaptation that was evolved for one purpose is co-opted for another
- Ex: invertibrates store phosphate in a matrix of calcium, which developped into hard tissue, which protects from predators
Speciation
The process of making new species
Biological species
Members of the same population that can interbreed and produce viable (living), fertile offspring. Not defines in terms of physical form
Transformation (anagenesis)
A species result from the transformation of its ancestor through accumulated changes over long periods of time
Divergence (cladogenesis)
One or more species arise from a parent species, which continues to exist. (promotes biodiversity)
Barriers to reproduction
- Geographical: populations cannot interbreed as they are physically separated
- Biological: restrict genetic mixing even when in the same area
Pre-zygotic Isolating Mechanisms
- prevent fertilization when different species attempt to mate (pre-fertilization)
- behavioural, habitat (ecological), temporal, mechanical, gametic
Behavioural
- special behaviours (signals) that are species specific
- Ex. courtship rituals, pheromones
Habitat (ecological)
- live in the same region, but occupy different habitats and niches
- Ex. red-legged frog - large ponds, yellow-legged frog - fast streams
Temporal
- timing of reproductive or mating seasons
- Ex. red-leg. frog - Nov-late April, yellow-leg. - late April-June
Mechanical
- reproductive parts are not anatomically compatible
- Ex. left curling snails vs riht curling snails, cat vs whale
Gametic
- gametes cannot survive the environment
- Ex. fish spawning
Post-zygotic Isolating Mechanisms
- prevent hybrid zygotes from developping into fertile individuals (post-fertilization)
- hybrid inviability, hybrid sterility (infertility), hybrid breakdown
Hybrid inviability
- zygote fails to develop or mature into an embryo
- Ex. eggs of red-necked and rock doves
Hybrid Sterility (Infertility)
- hybrid offspring develops, but is unable to produce function gametes/its own offspring (infertile)
- Ex. mule (donkey + horse)
Hybrid Breakdown
- the F1 generation are viable and fertile, but the F2 fail to develop (weak or infertile)
- Ex. domestic rice
Allopatric Speciation
- geographical isolation of subpopulations of the species, followed by natural selection and gene flow/drift, leading to the formaton of new species
- reason why the various races (subspecies) of animals almost never occupy the same territory
Sympatric Speciation
- formation of two of more descendant species from a single ancestral species in the same geographical area
- factors: chromosomal changes (plants) and non-random mating (animals)
- more common in plants: poliploidy
Divergent Evolution
Species that were once similar to the ancestral species diverge or become increasingly distinct
Convergent Evolution
Similar traits arising because each species independently adapted to similar environmental conditions, NOT because of a common ancestor
Coevolution
Organisms that are tightly linked with one another and have evolved gradually together, each responding to changes in the other. Ex. predators, prey, parasites
