Week 2 Biology- evolution and natural selection

Evidence for Evolution

(1) The fossil record - physical evidence of past life (2) Biogeography - patterns in the geographic distribution of living organisms. (3) Comparative anatomy and embryology - similar body structures, growth, and development of major groups of organisms. (4) Molecular biology - examination of life at molecular level. (5) Lab and Field Studies - using scientific method to study evolutionary mechanisms.

3 elements important to an organism's fitness

1: An individual's fitness is measure relative to other genotypes of phenotypes in the population 2: fitness depends on the specific environment an organism lives in. The fitness value of having one trait vs another depends on the environment 3:Fitness depends of an organism's reproductive success compared to the other individuals in the population

Why cant organisms reach a level of ultimate fitness if they are constantly evolving to be more fit for their environment?

1: The environment they live in is constantly changing. Natural selection may be too slow to adapt the organisms in a population to such a constantly moving target. 2: Variation is needed as the raw material of selection, that is the first condition of natural selection. 3: there may be different alleles for a trait, each causing individuals to have the same level of fitness. Each allele represents an equally fit solution to the environmental challenges.

2 patterns Charles Darwin Noticed

1: the finches he thought were of the same species but exhibited different physical traits were really 13 unique species. 2: at every location there were many similarities between the fossils of extinct species and the living species in the area

3 conditions necessary for natural selection:

1: there must be variation for the trait within the population 2: the variation must be inheritable 3: individuals with one version of the trait must produce more offspring than those with a different version of the trait.

Evolution by migration (or gene flow)

A change in allele frequencies cause by individuals moving into or out of a population

Evolution by natural selection

A change in allele frequencies that occurs when individuals with one version of a heritage trait have greater reproductive success than individuals with a different version of that trait.

Genotype

A genotype is an individual's collection of genes. The term also can refer to the two alleles inherited for a particular gene.

Population

A group of organisms of the same species living in a particular geographic area

Fittness

A measure of the relative amount of reproduction of an individual with a particular phenotype compared with the reproductive output of individuals of the same species with an alternative phenotype.

Radiometric Dating

A method of calculating the age of an organism's remains by using by measuring the relative amounts of the radioactive isotope and its left over decay product in the rock where the fossil was found. Each isotope has its own half life and each has its own limitations.

Phenotype

A phenotype is an individual's observable traits, such as height, eye color, and blood type. The genetic contribution to the phenotype is called the genotype.

Evolution by genetic drift

A random change in allele frequencies in a population.

Allele

An allele is a variant form of a gene. Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome.

Evolution by mutation

An alteration of the base-pair sequence of an individual's DNA. When this alteration occurs in DNA that codes for a particular gene it can cause a change in the DNA sequence that may change the alleles.

Why are both Darwin and Wallace credited with the discovery of evolution by natural selection?

Because they both reached the same conclusion. Darwin did first but never published it and their ideas were presented in conjunction at the Linnaean Society of London.

Pre-Darwinian beliefs:

Before Darwin many people believed that all species had been created separately, at the same time, and once they existed they never changed and never went extinct.

True or false: organisms in a given species can interbreed with each other as well as closely related species.

False. Individuals within a species can ONLY interbreed with others members of the same species.

Evolution

Genetic change in a population over time that makes it stronger and enable them to survive better. Evolution isn't genetic or physical changes in individuals, rather it is change in the proportions of the alleles in the population as a whole

Jean-Baptiste Lamarck

He suggested that living species may change over time through the use or disuse of certain features or characteristics in a species.

Artificial Selection

Humans can cause an artificial natural selection by breeding organisms which have a specific trait that they desire. Such as crops that produce more goods, or cows that give the most milk. It meets the 3 requirements for natural selection.

George Buffon:

In 1778 He suggested that the earth must be 75,000 years old because he estimated that it would take at least 75,000 years for the planet to cool from a molten state

Charles Lyell

In 1830 he argued that geological forces had shaped the earth and were continuing to do so, producing mountains, valleys, cliffs, and canyons through gradual but continuous change.

Directional Selection

In directional selection, the individuals with an extreme range of variation of a trait in a population have a higher level or fitness. Example: Farmers selectively breed cows with the highest milk production

What distinguishes genetic drift from natural selection:

In genetic drift that the change in allele frequencies is not related to the allele's influence on reproductive success. For example, a cleft chin trait from genetic drift won't effect an individual's ability to reproduce.

Georges Cuvier

In the 1790s discovered fossil remains of species that no longer existed and did not have any obvious similarities to existing ones. The fossils he discovered proved that extinction was a fact

Disruptive selection

In this type of selection the individuals on either end of the extreme phenotype spectrum have the highest fitness. Example: Medium sized fish get outcompeted for territory by the larger fish, but the small fit are able to sneak into the nests of larger fish to fertilize eggs without being detected. Both large and small fish are fit

Differential Reproductive Success

Individuals with the version of a trait most suited to reproduction in their environment generally have more offspring than those individuals with other versions of the trait because they are better suited for survival and thereby reproduction.

Migration/Gene flow is influenced by:

It is influenced by the mobility of the organisms and by barriers such as mountains, rivers, and even human activity like transporting animals from one location to another.

Important to remember about mutation as evolution mechanism:

Multicellular eukaryotic organisms have two cell types. somatic cells and reproductive cells. Somatic cells, the cells forming the body of the organism- are not passed from parent to offispring. Only mutations in the reproductive cells can be inherited.

4 mechanisms that drive evolution:

Mutation Genetic drift Migration Natural selection

What causes genetic variation in a population?

Mutations among individuals or groups of individuals are the ultimate source of genetic variation.

Functional Shifts

Often, structures are enhanced or elaborated on by natural selection beyond the initial function because they enhance overall fitness by serving some other purpose.

Theory of evolution started with:

Perhaps the island finches resembled the mainland species because they used to be part of the same mainland population. Maybe Overtime they separated and diverged from the original to form a new but similar species.

Mutation is critical to natural selection because:

Some mutations can confer higher fitness and survival capability. All variations- the raw material for natural selection- must come initially from mutations.

Sexual Selection

Some traits lead to greater reproductive success because they make the individual more attractive to the opposite sex. These traits satisfy the three conditions and so natural selection for making success is called sexual selection.

Fossils

The physical remains of organisms that have been preserved over time as a result of special environmental conditions.

Biogeography

The study pf the distribution patterns of living organisms around the world and over the course of history. Animals adapt to better fit their environment, they do not go out in search of a better environment for their current state.

Inheritance and heritability

The transmission of traits from parents to their children through genetics is inheritance.

Evolution occurs when...

There is a change in allele frequencies within a population. It can occur by the 4 different mechanisms.

Stabilizing selection

This occurs when individuals with intermediate phenotypes are the most fit. Example: Babies who weigh 7-8 lbs are best suited for survival compared to those who weigh less and more than that range.

True meaning of "Survival of the fittest"

This phrase is actually referring to an organisms reproductive success. Those who are best fitted for the environment and reproduce the most will survive.

Hardy-Weinberg Law

This principle/law explains why a recessive trait does not become rarer in a population or eventually phase itself out. In relies on 2 conditions:there is random mating among individuals, and there is no evolution. If these are met then the allele frequencies will not change over time and recessive traits wont decrease in frequency.

Adaption

This term refers both to the process by which organisms become better matched to their environment and to the specific features that make an organism more fit.

By analyzing the fossil remains...

We can reconstruct what organisms looked like from a long time ago and we can learn how organisms were related to each other, and understand how groups of organisms evolved over time.

Bottleneck effect

When a population is effected by famine, disease, or rapid environmental change it can causes many individuals to die. This rapid population reduction is a bottleneck and the remaining population may not have the same allele frequencies as the original population leading to evolution by genetic drift.

Founder effect

When a small number of individuals leave a population they become the founders of a new isolated population. The founding population may have a different allele frequency than the source population because all genetic material is from the founding members.

Natural Selection on behaviors

Yes, natural selection does impact behavioral and mental traits. Since there is a genetic component to them they can be altered and developed by natural selection