Principles of Evolution

• Evolution requires existing life and explains changes, not the origin of life itself.
• Traits arise from mutations, not necessarily for survival; selection acts on existing variations.
• Disease genes can persist if their effects manifest after reproduction.
• Humans continue to evolve due to environmental and trait-based adaptations.
• Evolution adapts species to their environment, traits may come at a cost and may not improve the species.
• Evolution can be gradual or punctuated by rapid changes.
• Extinction is a natural process, contributing to species turnover.
• Evolution explains diversity through allele frequency changes in populations and is visible on a micro scale.
• Evolution studies include inheritance, quantitative genetics, and adaptations.
• Paleobiology examines large-scale evolutionary changes and studies the fossil record.
• Integration of genetics and morphology studies developmental patterns and evolutionary transitions.

Charles Darwin

• Charles Darwin journeyed around the world, taking notes and gathering samples for study.
• Darwin visited the Galapagos Islands and observed the unique species of each island.

Ideas That Inspired Darwin

• Some species go extinct.
• Earth is older than believed and changes over time.
• Species adapt over time.
• Competition leads to adaptation.

Curvier

• Curvier compared fossils to existing species, noting similarities and differences.
• He recognized that some species have gone extinct for example, extinct mastodons.

Lyell

• Lyell posited that landforms change due to slow geological processes, not catastrophes.
• Geological processes like forming mountains and canyons takes a long time.

Lamarck

• Species change over time through transmutation, with traits acquired and passed on.
• Darwin was influenced by Lamarck's ideas on inheritance
• Epigenetics shows that DNA interpretation can change and be inherited.

Malthus

• Population growth outpaces resources, leading to competition and adaptation.
• Competition will allow the best suited to acquire resources, and pass traits to the next generation.

Darwin's Theory

• Artificial selection, where humans choose traits, shows that species can change drastically.
• Natural selection can drive drastic changes in nature the same way.

Galapagos Finches

• Finches adapted to different food sources: big beaks for nuts, small beaks for insects.
• The environment causes species to adapt from ancestral finches that may have come from the mainland.
• Common ancestor for all life on earth.

Alfred Russel Wallace

• Alfred Wallace independently developed a theory of natural selection.
• Both Darwin's and Wallace's ideas were published under evolution.

Natural Selection

• Natural selection acts on existing, heritable variations in a population to improve their chance of survival.
• Struggle for existence eliminates unfavorable traits.
• Life is associated with the environment the species lives in.

Darwin's Finches: A Case Study

• Island species differ despite proximity
• The Galapagos islands are remote, limiting gene flow and fostering unique adaptations.
• Adaptation radiation of finces: Ancestral species diversified into new species filling ecological niches.

Heritability: Beak Gene

• If a gene is linked to an adaptive phenotype, variation can be inherited.
• Natural selection leads to the inheritance of traits, with traits organisms need to survive.
• Natural Selection Chooses particular traits that have to show reproductive success.

Key Concepts

• Evolution through natural selection happens if there is trait variation, heritability, differential survival, and environmental influence.

What Darwin Didn't Know

• Darwin did not know about DNA, heritability, or how traits skip generations.

Inheritance Theories: Darwin and Mendel

• Mendel solved Darwins problem of genetics.

Blending Inheritance

• The idea that offspring have a mix of parents and their traits.
• Variation would be reduced overtime.

Lamarck: Inheritance of Acquired Traits

• Traits that were favourable were passed onto the next generation and less favourable may not.

Gregor Mendel

• Mendel tested blending vs particulate inheritance.
• He discovered several discrete traits in peas that could be followed from one generation to the next.

Mendel's Experiment

• Mendel used true-breeding strains and focused on single traits, collecting quantitative data.
• He discovered that yellow seeds were dominant over green in kids
• First generation showed dominant traits.

Segregation

• Second generation was a mix after self fertilization but green traits also re-emerged.
• Any of these traits there were 2 factors individuals inherited that governed phenotypes (allele).
• He showed they came back due to traits being split during the formation of gametes.

Mendel's Hypothesis

• Adults have two copies of factors (genes) that separate and recombine to determine phenotype.
• Dominant traits mask recessive traits.
• Alleles separate during gamete formation, resulting is differing alleles that are passed on.

Monohybrid Crosses

• The probability of inheriting alleles follows random gamete combinations.
• Genetic outcomes are predicted statistically.

Test Crosses

• Test crosses with homozygous recessive individuals reveal recessive alleles in dominant phenotypes.
• Mendel's laws were observed during anaphase 1.

Dominance

• Dominance not always universally observed.
• Incomplete dominance produces intermediate phenotypes where the other allele in non-functioning.
• Codominance means that alleles have equal effects and are both expressed not merged.

Poly Allelic

• There can be more than 2 alleles for genes.
• Increased variability in immune system.
• It also increases a larger number of survivability

Mendelian Segregation

• Genetic variation is preserved in Mendelian segregation.
• This provides a range of phenotypes.

Complex Traits

• Complex traits have phenotypes that exist on a spectrum.
• This may be due to the fact these are polygenic traits (more than one gene controls it).
• The more genes, and outside factors, the more phenotypes we see.

Allele Frequency

• Maths will be based on Allele frequencies rather than individuals
• It is not always the same ratio as a single cross.

Evolution

• Includes Mutation, MIgration, genetic drift (randomness of survival).
• May change Phenotyic ration.

Hardy-Weinberg Conditions

• Conditions needed in order for there to not be evolution:
• No new additions to existing alleles , no gene flow (migration, in or out), population is very big(infinite), no evolution is taking place, no random mating.

Natural Selection

• Natural selection doesn't act on variants that will lead to reproductive success.
• Allele frequencies can't be changed through mutations .

Allele Frequencies

• If all conditions of Hardy-Weinberg is met it will reman forever with randomly coming together gametes.
• If not it will cause genetic drift.

Evolution by Randomness

• Evolution by randomness will create the next generation.
• smaller population more, Impacts (change in alle frequencies due to chance).

Bottlenecks

• Bottlenecks : individuals that are surviving all have an allele frequency that isn't the same as the starting population.
• Will not allow population to re populate to where is ones was previously.

Founder Effect

• Founder are dispersing and settling in new areas.
• original phenotype will be altered.

Population Divergence

• allele will be fixed.
• The more genetic drift we have the more likely alleles will get fixed.

Bottleneck

• Founder are for when one is trying to create a new population
• Bottlenecks are when the original population is.

Affects of Random Mating

• affects genotype frequencies rather than allele frequencies.
• may result in Increasing homozygosity (recessive).

Natrual Selection

• Natrual Selection acts on frequencies between the parental and offspring by 3 individuals vary.
• Survival and reproduction is not random
• Variation is being passed on offspring (traits will continue to emerge).

Pattern For evolution

• Pattern are, Directional selection: One extreme phenotype is selected. Stabilizing selection: Selection favouring intermediate phenotype (ex, Disruptive selection; Favouring for both extreme phenotypes : intermediate phenotypes

Directional Selections

• If we apply a fitness curve that is favouring extreme large body size than small body, we expect to see a shift in the phenotype distribution
• Lsee is a shift.

Stabilizing Selection

• Stabilizing selection : is for the better of an extreme type.
• We don't get an evolution of the trait mean, but reducting vairaiton in favour of the

HeteroZygote Advantage

• Tend to have a survival advantage over other homozygous genotype
• Example: Sickle cell anemia and malaria >crystallisation of hemoglobin at low o2 concentration

Disruptive selection

• curve is low in the intermediate phenotypes.
• end towards a large number of sides.

Selection Manifest

• manifest: Reproductive success is dependent on what biological sex one is.

Sexual Selection

• is that weather ot not you can succed at baby making other organisium.
• has an impact on sexual selection.

Unsexual selection

• differences, selection hapening between the members of the same.
• opposte site, males and females(
• selection
• for opp.