Evolution

Georges Louis Leclerc, Comte de Buffon (1707-1788)

Georges Louis Leclerc, Comte de Buffon (1707-1788)

One of the first to publicly challenge the idea that life forms are unchanging

Noted the similarities between humans and apes, speculating a common ancestor and suggesting species do change over time

Georges Cuvier (1769-1832)

Found each layer of rock is characterized by a unique group of fossil species

• the deeper the rock (older), the more dissimilar they are from modern life

• from layer to layer, found evidence that new species appeared and others disappeared over time

• showed species could be extinct

Paleontology

study of ancient life through the examination of fossils

Catastrophism

the idea that many destructive natural events in the past (floods, volcanic eruptions) were violent enough to have killed numerous species at a time

• catastrophes corresponded to the boundaries between layers of rock studied by Georges Cuvier

Charles Lyell (1769-1832)

Uniformitarianism

geological processes operated at the same rates in the past as they do today. Suggested geological changes are slow and continuous rather than catastrophic, and can happen over a long period of time and could result in substantial changes (e.g., forces that build and erode mountains)

Jean-Baptiste Lamarck (1744-1829)

the first scientist to recognize that the environment plays a key role in the evolution of species. Believed in evolutionary change and improvement of individual species. He further postulated the theory of inheritance of acquired traits.

Erasmus Darwin (1731-1802)

English physician, turned down being the doctor to the king, proposed that all life may have a single source. Grandfather of Charles Darwin

Darwin’s Voyage of Discovery

December 1831 (for about 5 years)

Voyage to South America on the HMS Beagle

Observed, recorded, collected specimens

Patagonia

Observed by Darwin

Collected 2 species’ fossils that were identified later as large versions of armadillo and sloth that still inhabited the continent

Darwin thought the fossils represented ancestral forms of the living organism

Unearthed Glyptodon with resemblance to modern armadillo and Megatherium with resemblance to modern sloth

Galapagos Islands

Darwin collected 26 birds (including large number of finches and 3 species of mocking birds)

Darwin found the ____________ to be inhabited by flying organisms, and land animals that could survive long periods at sea with no food or fresh water

Darwin’s Shaping of the Theory of Evolution

Homologous and Analogous Features

Vestigial Features and Anatomical Oddities

Artificial Selection

Survival of the Fittest

Homologous Features

body parts of organisms with entirely different functions for similar structures

Analogous Features

body parts shared by many organisms and serving a common function, with different internal anatomy

Vestigial Features

structures that serve no useful function but are homologous to fully functioning structures

ex. appendix, ear muscles (humans have the muscles to move years but don’t use them like other animals due to lack of useful function), tail bone, split bone in horse leg, snake leg bones, whale hipbone

Artificial Selection

selecting individuals with the most desirable traits and mating them to produce next-gen.

all species possess inherited variations that can be selected to change the species in desirable ways

Survival of the fittest

everything producing more offspring than are able to survive so favourable variations would tend to be preserved, and unfavourable ones destroyed

competition between individuals in a species, those who survive have favourable traits which will be passed on

gene

portion of DNA that codes for traits

loci

location of a gene on the DNA molecule

Allele

different forms of a gene

homozygous

two identical alleles for a trait

heterozygous

two diff alleles for a trait

genome

complete set of all alleles possessed by an individual organism

all members of the same species have the same genome

Genotype

the set of alleles

genome of a species will be the same, but their specific genotype (combination of alleles) will be different

Phenotype

observable taints coded by the genotype

natural selection works on the phenotype, thereby altering the genotype

Genetic Variation

variation within a species is a result of the variety and combination of alleles possessed by individuals

sexual reproduction results in random recombination of different alleles and results in a high degree of genetic diversity within most populations

Gene Pool

the genetic information of an entire population

population

members of the same species living in the same region

allele frequency

the proportion of gene copies in a population of a given allele

evolutionary change can be measured in part by looking for changes in ______________

How Hardy-Weinberg principle came to be

Punnett posed questions to mathematician, Godfrey Hardy about allele frequencies and he wrote the solution on a napkin

in meantime, a German physician Wilhelm Weinbery formulated the same solution

What does the Hardy-Weinberg Principle show

that allele frequencies will not change from generation to generation as long as certain conditions are met like a large population, equal mating opportunities, no mutations, no migration and no natural selections (equal chance of reproductive success)

p in H-W equation

frequency of allele A

q in H-W equation

frequency of allele a

Microevolution

when frequency of an allele changes, occurs before evolution

evolutionary changes that occur at the species level

Macroevolution

evolution of population

Mutation

change that occurs in the DNA of an individual which can affect a gene pool

can cause a trait that will benefit that individual in a population

gene will be passed down and that trait will appear more often

Gene Flow

movement of alleles from one population to another as a result of migration of individuals

ex. when a grey wolf (very large territories) travels to another population to find a mate

Non-random Mating

Preferred Phenotype or Inbreeding

Preferred Phenotype

non-random mating

females often choose mates based on their physical and behavioural traits

want their offspring to benefit from mate’s genes

only individuals that mate will contribute to the gene pool of the next generation

Inbreeding

non-random mating

when closely related individuals mate

increases occurrence of homozygous individuals

can also cause an increase in harmful recessive alleles

Genetic Drift

The change in frequencies of alleles due to chance events

affects smaller populations

better chance certain alleles will show up more often in the population is smaller

The founder effect

Genetic Drift

the change in gene pool when a few individuals start a new, isolate population

will carry some, not all alleles from population, if the alleles they carry are rare, more likely to increase in the population

happens often in islands

e.g. polydactylism in Amish communities

Bottleneck Effect

gene pool change the results from a rapid decrease in population size, can be cuz of starvation, disease, human activates, natural disasters, etc.

Survivors likely have only a fraction of the alleles that were present in the original population

e.g. animals close to extinction and rejuvenated have low genetic diversity

Natural selection

causes change in allele frequencies of a population, which can lead to evolutionary change

How does natural selection occur

by having a single allele that gives even a slight, yet consistent, selective advantage, the frequency of the allele in the population will increase

that individual will survive to reproductive age and pass on that allele to the next-gen

types of Natural Selection

stabilizing selection

directional selection

disruptive selection

factors that change allele frequencies

mutation

gene flow (migration)

genetic drift

natural selection

Stabilizing Selection

favors the intermediate phenotype and eliminates the extreme

Directional Selection

favours the the extreme phenotype, and occurs when there is an environmental change or if there is a new niche to exploit

Disruptive selection

favours both extremes in the phenotype eliminating the intermediate

sexual selection

competition between males through combat or visual displays

_______________ theory: males will compete with each other to access mates and females will be choosy

sexual dimorphism, male-male combat, sperm competition, infanticide, female choice

Adaption

a trait that increase the reproductive fitness of its possessor

giraffe neck fighting

before classifying something as an adaption:

1. determine what a trait is for

2. show that the individuals possessing that trait contribute more genes to future generations than organisms lacking it

Sexual Dimorphism

a difference between males and females of a species

Reproductive success

having a better chance at passing your genes on in future generations

challenges: surviving long enough to reproduce and finding a mate

Intrasexual Selection

males compete, and females choose a winner

types: combat, sperm competition, infanticide

Intersexual Selection

males advertise by singing, dancing, or showing off and females choose male with best display

Combat

the most obvious form of male-male competition for mates, favours traits like large body size, weaponry, armour and tactile cleverness

Sperm Competition

male-male competition does not necessarily stop when copulation is over, mating success actually refers to if his sperm fertilizes the eggs

if female mates with two males in a short time, then the sperm will be in a race to the egg

Adaptions for Sperm Competition

• Release more sperm (better odds)

• males guarding their mates

• prolong copulation

• deposit a copulatory plug

• relase pheromones that reduce the female’s attractiveness

Infanticide

competition amoung males continues even after conception

in lions, female will not return to breeding until her cubs are weaned, so if a new male enters the pride, he will kill the cubs to increase his reproductive success

Female Reproductive success against infanticide

defend cubs from males (often results in their own death along with cubs) or spontaneously abort any pregnancies in progress when a new group of males gains residence in a pride (reduces the amount of energy she invests carrying the cubs to term, just to have them killed anyway)

Fossil Record

the remains and traces of past life that are found in sedimentary rock; it reveals the history of life on Earth and the kinds of organisms that were alive in the past

Burgess Shale Fossils Beds in BC

where fossils of animals that lived in an ancient ocean during the Cambrian period, over 500 years ago were found

preserved some of the earliest animals with hard parts to be seen in the fossil record

transitional fossil

fossils that shows intermediary links between groups of organisms and shares characteristics common to two separate groups

helped scientists better understand the evolutionary process and relationships between groups of organisms

link fossils of the past and present

Vestigial Structure

a structure that is reduced version of a structure that was functional in the organism’s ancestors

biogeography

the study of the past and present geographical distribution of species population

supports Darwin and Wallace’s hypothesis that species evolve in one location and then spreads out to other regions

Speciation

the formation of an entirely new species

Reproductive Isolation

when populations become two species

occurs when there is little or no gene flow between them

can be pre-zygotic or post-zygotic

Pre-Zygotic

Also called pre-fertilization barriers

can impede the mating of species and prevent fertilization of eggs if individuals from different species attempt to mate

Ecological/Habitat Isolation

Pre-zygotic: Prevention of mating

when species occupy same general region, but separate habitats, or separate niches of the same habitat, do not encounter one another to reproduce

ex. woodchucks and squirrels in alpine meadows

Temporal Isolation

Pre-zygotic: Prevention of mating

compatible species inhabit an overlapping range but their reproductive cycles occur at different times

more common in plants

Behavioral Isolation

Pre-zygotic: Prevention of mating

a distinct mating ritual by one closely related species not being recognized by another species

Mechanical Isolation

Pre-zygotic: Prevention of fertilization

Structural differences in reproductive organs can prevent copulation

Gametic Isolation

Pre-zygotic: Prevention of fertilization

If the gametes ever meet, they will rarely fuse to form a zygote. Molecular level

Post-Zygotic

sometimes the sperm of one species can successfully fertilize the egg of another species and produce a zygote

___________ prevents these zygotes from developing into viable, fertile individuals

types: hybrid inviability, hybrid sterility, hybrid breakdown

Hybrid Inviability

the development of the zygote may stop due to the genetic incompatibility

ex. goat and sheep embryos die before development cuz mitosis is prevented

Hybrid Sterility

when two species mate and produce hybrid offspring that is sterile (meiosis prevents normal gametes-chromosomes may differ in number or structure)

Hybrid Breakdown

two species mate to produce hybrid offspring that are fertile and can mate, but their offspring are sterile and weak

ex. cotton plants produce fertile hybrids but the offspring die as seeds

more in plant kingdom

Types of Speciation

Allopatric

Sympatric

Allopatric Speciation

species evolving differently due to geographical isolation

ex. founder populations after being separated from OG population

Types of of barriers that create allopatric speciation

• large river or canyon for small rodents or snakes

• large bodies of water for weak birds

• dams, canals or major highways for aquatic species

Sympatric Speciation

evolution of population in same geographical location into different species

some populations split into separate gene pools and continue to share similar geographical location

Adaptive Radiation

Form of allopatric speciation, where there is diversification of a common ancestor species into a variety of differently adapted species

occurs in islands often since there are a number if new niches able to be exploited

greater biodiversity

ex. Darwins Flinches

Forms of Evolution

Divergent Evolution

Convergent Evolution

Divergent Evolution

Organisms that were once similar to an ancestral speices diverge, or become more distinct

adapted to diff environmental conditions

Convergent Evolution

similar traits arise in unrelated species because each species have independently adapted to similar environmental conditions

not common ancestor

Speed of Evolutionary Change

gradualism

punctuated equilibrium

Gradualism

model of evolution that views evolutionary change as slow and steady, before and after divergence

Punctuated Equilibrium

model of evolution that views evolutionary history as long periods of stasis, or equilibrium, that are interrupted by periods of divergence

Archaeopteryx

show transitional stage in the fossil record cuz this species has characteristics of both reptiles (dinos) and birds

Embryology

the study of early-pre-birth stages of an organisms development

used to determine evolutionary relationship between animals

similarities between embryos in related groups (such as vertebrae) point to common ancestral origin

DNA and common ancestors

since DNA carries genetic info, it can be used to determine how closely related two organisms are

similar DNA patterns mean that these DNA sequences must have been inherited from common ancestors

The Theory of Evolution by Natural Selection

1. individuals within species vary in many ways

2. some variability can be inherited

3. every generation produces way more offspring than can survive and pass on variations

4. populations of species tend to remain a stable size

Rev. Malthus

population increases exponentially and food linearly

as human popu continues to increase, food supply won’t be able to keep up (critical point when popu and food lines meet) and will run out and will lead to famine death and destruction

Wallace

father of biogeography

studied geographic distribution of species, learned that the fittest survived and reproduced, passing traits on to offspring

Huxley

studied natural history with a focus on marine invertebrate

thought that large-scale mutations—evolutionary jumps termed “saltations”—were more important than variations acted upon by natural selection

defended and advocated for Darwin's theory of evolution by natural selection

Darwins Bulldog

Radiometric Dating

method used to establish how old an object is by measuring amount of radioisotopes the object contains against the decay product it contains

when an organism dies it stops taking in carbon-14 and the existing isotopes decays with a characteristic half-life (5730-years)