Evolution

Patagonia significance

Patagonia significance

Darwin collected species fossils that were identified later as large versions of modern animals. This helped him create his theory of evolution

Homologous features

Similar structure different function inherited from the same ancestor (Ex. arms of a human and ape)

Analogous features

Different structure similar function, despite not evolving from the same ancestor (Ex. Arm of bat and arm of seal)

Vestigial features

Structures that serve no longer serve a useful function common in animals (Ex. Hipbone in a whale)

Artificial selection

When selecting individuals with the most desirable traits and mating them to produce the next generation, all species possess inherited traits that can be selected to change the species in desirable ways

Survival of the fittest

When animals produce far more offspring than are able to survive, favourable traits would tend to be preserved, and unfavourable ones to be killed. The result is the formation of a new species with only desirable traits

How is natural selection significant to Darwin

In the struggle to survive, the most favourable traits are inherited by the succeeding generations

How is artificial selection significant to Darwin

Helped him realize that If people could alter the appearance and behaviour of species through artificial selection, then the environment could have a similar selective effect on wild species.

Genetic Variation

The quantity of DNA and the number of genes are variable among a species. Variation within a species is a result of the variety and combination of alleles possessed by individuals

Gene pool

The genetic information of an entire population

Allele frequency

The frequency of genes in a population of a given allele

Hardy-Weinberg Conditions

• The population is very large

• Mating opportunities are equal

• No mutations occur

• No migration occurs

• No natural selection occurs – all individuals have an equal chance of reproductive success

What causes evolution?

Genetic mutations that result in more favourable traits. Sexual reproduction allows for variety within the gene pool and changes in allele frequencies.

Microevolution

The frequency of an allele changing

Factors that cause microevolution

• Mutation

• Gene flow (migration)

• Non-random mating

• Genetic drift

• Natural selection

Gene flow

Movement of alleles from one population to another as a result of migration of individuals (Ex. a grey wolf travels to another population to find a mate)

Non-random Mating

Mating among individuals on the basis of mate selection for a particular phenotype or due to inbreeding. Females often choose mates based on their physical and behavioural traits, in order for their offspring to benefit from their mate’s genes

Genetic drift

The change in frequencies of alleles due to chance events

The founder effect

The change in gene pool when a few individuals move and start a new isolated population. More likely to increase rare alleles in the population

The bottleneck effect

Gene pool change that results from a rapid decrease in the population size. Can be caused by starvation, disease, human activities, natural disasters. Survivors likely have only a fraction of the alleles that were present in the original population

Types of Natural selection

Stabilizing, Directional, Disruptive

Stabilizing selection

Favours the middle phenotype and eliminates the extreme phenotypes, keeping the population fairly constant

Directional selection

Favours the extreme phenotype, occurs when there is an environmental change

Disruptive selection

Favours both extremes in the phenotype, eliminating the intermediate

Adaptation

A trait that increases the reproductive fitness of its possessor. More of their genes are passed on since they are more likely to survive to reproductive age

Sexual selection

Males will compete with each other over access to mates, and therefore females will be choosy

Sexual Dimorphism

Physical difference between the males and females of a species. Aids the males in appealing to a female (Ex. Antlers in male deers)

Intrasexual selection

Males compete, and then females choose the winner

Intersexual selection

Males advertise by singing, dancing, or showing off, then female chooses male with best display

Types of Intrasexual selection

Combat, Sperm combat, Infanticide,

Combat

Two males physically fight for a mate.

Sperm competition

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

Solutions to sperm competition

• Release more sperm

• Guarding mate

• Prolonged copulation

• Deposit a copulatory plug to block other sperm

• Apply pheromones to make female smell less attractive

Infanticide

Males will kill babies/unborn children to a female in order to coapulate and increase their reproductive success

Speciation

The process by which new species evolve from existing ones. Occurs when two populations may separate and become distinct from one another due to a lack of gene flow

What are reproductive isolating methods

Methods that prevent gene flow between populations

Types of reproductive isolation methods

Pre-zygotic and Post-zygotic

Types of pre-zygotic isolation

Behavioural, Habitat, Temporal, mechanical, and gametic

Behavioural Isolation

Species-specific behaviour that prevents different species from mating (Ex. mating calls, pheromones)

Habitat Isolation

Species that live in different habitat’s/climate are not likely to mate (Ex. dry vs wet climate)

Temporal Isolation

Species with time differences will not mate with one another (Ex. mating seasons, nortural vs diurnal)

Mechanical Isolation

Species may mate, but due to different genital anatomy, the eggs cannot fertilize (Ex. the eggs may be farther than the sperm can swim)

Gametic Isolation

When egg and sperm of different species meet, they fail to fertilize

Pre-zygotic Isolation

Impedes on mating between species and fertilization of eggs

Post-zygotic Isolation

Methods that prevent organisms born of 2 different species from reproducing

Types of post-zygotic isolation methods

Hybrid Inviability, Hybrid Sterility, Hybrid Breakdown

Hybrid Inviability

The resulting organism dies before reaching the reproductive stage, caused by genetic incompatibility in the chromosome

Hybrid sterility

The resulting organism is sterile, caused by different chromosome shapes and numbers from parent gametes

Hybrid Breakdown

The organism manages to survive to the reproductive stage, but its children do not

Types of speciation

Sympatric and Allopatric

Sympatric Speciation

Populations within the same geographical area become reproductively isolated (Ex. Plants)

Allopatric Speciation

A population is split into isolated groups by a geographical barrier. The gene pool differs greatly between the two, and they are no longer able to reproduce.

Examples of Allopatric Speciation

The founder effect

Adaptive Radiation

Organisms evolve rapidly from an ancestral species into a several new forms. Happens when a change in the environment makes new resources available

Divergent Evolution

Organisms that were once similar to an ancestral species diverge, or become more different. Adapt to different environmental conditions

Convergent Evolution

Similar traits appear in unrelated species because each species has independently adapted to the environmental conditions, NOT because they have a common ancestor (Ex. Bird and bat wings)

Gradualism

Evolution occurs through gradual, slow changes

Punctuated Equilibrium

Evolution occurs through long periods of balance, with sudden periods of change

Beneficial mutation

mutation that has a positive effect on the organism’s reproductive fitness

Harmful mutation

mutation that causes harm to the organsisms reproductive fitness

Neutral mutation

mutations that are nether beneficial nor bad for the organism’s reproductive fitness

Radiometric dating

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

Biogeography

The study of past and present geographical locations of species

Georges Louis Leclerc, Comte de Buffon

The first to challenge the idea that life forms are unchanging, and that Earth was 6000 years old.

Georges Cuvier

Founded palaeontology and proposed catastrophism as an explanation for fossil history. Found evidence that new species appeared and others disappeared over the passage of time.

Catastrophism

The idea that catastrophes such as floods, diseases, and droughts periodically destroyed species, and allowed species from neighbouring regions to repopulate the idea

Charles Lyll

Proposed uniformitarianism, and said that slow, subtle processes happen over a long period of time, but result in drastic changes

Uniformitarianism

Geological processes operated at the same rates in the past as they do today.

Jean-Baptiste Lamarck

Proposed that species increased in complexity over time, until they achieved a level of perfection, and that they would become progressively better adapted to their environment. First to propose the theory of acquired traits. Stated that features that organisms used became stronger and more prominent than others (Ex. Elephant trunk)

Theory of acquired traits (Lamarck)

Characteristics acquired during an organisms lifetime can be passed onto offspring

Erasmus Darwin

Proposed that all life may have a single source

Wallace

Reached similar conclusions to Darwin

Malthus

Proposed that populations produced far more offspring than the food supply could handle, inevitably resulting in disease and starvation

Huxley

Where Darwin had seen evolution and a slow, gradual, continuous process, Huxley thought that an evolving lineage might make rapid jumps, or large-scale mutations