Evolution

Speciation

Speciation

The process of how a new species is created

Evolution

The change in the heritable characteristics of a species over time

The Mechanisms of Evolution

Natural Selection, Genetic Drift, Gene Flow, Genetic Mutations

Lamarckian Evolution

Organisms pass down traits that they develop during their lifetime. This is incorrect because only genetic information is passed down and an organism cannot alter it’s genes

Descent with Modification

When organisms reproduce, their offspring will inherit most of their parents traits, but random mutations and variation during the reproductive process means that the offspring will have some genetic differences from their parents and siblings.

Common Descent

All living things are distantly related, Descent with Modification caused the biodiversity we see today.

Components of Natural Selection

Variation, Competition, Fitness, Adaptation.

Variation

A Component of Natural Selection. Organisms of the same species (and, due to Descent with Modification, same parents) can have differences (variations). Genetic Variations can be passed down and inherited.

Competition

A Component of Natural Selection. Competition refers to organisms having to compete with other organisms in order to survive or reproduce. Competition is more intense in environments with limited resources.

FItness

A Component of Natural Selection. Fitness refers to an organisms ability to survive and reproduce. Because of Variation, some organisms have traits that make them better at surviving and reproducing. Fitness is context-dependent, a trait that is beneficial in one environment may be neutral or harmful in another.

Adaptation

An adaptation is any Variation that helps a species survive. Overtime populations change so there is a higher percentage of organisms with faborable traits (adaptations). This is because organisms with more adaptations tend to have higher fitness, which allows them to reproduce and pass on their adaptations.

Natural Selection

The process by which Variations that improve an organisms Fitness (Adaptations) tend to spread. It works because Organisms with helpful Variations are more likely to survive and reproduce, passing the helpful Variations down to their offspring.

Structural Adaptations

Variations in the body of organisms (Ex: Color, Shape, Size). Examples of this are Mimmicry and Camouflage.

Behavioral Adaptations

Variations in the instincts of organisms.

Physiological Adaptations

Variations in the metabolic processes (such as digestion or antibiotic resistance) of organisms.

Selective pressures

Environmental factors (such as predation, physiological pressure, and sexual pressure) that determine what traits are beneficial and detrimental to an organisms survival.

Predation

Predation is a type of selective pressure. Traits that cause prey to get eaten are selected against and traits that cause predators to eat prey are selected for.

Sexual selective pressure

Sexual selective pressure is a type of pressure which selects for traits that assist in attracting a mate, impregnating a mate, and competing with other organisms for a mate.

Population

A group of organisms of the same species in the same area at the same time

Biological Species Concept

This definition defines a species as a group of potentially interbreeding organisms that can produce fertile offspring. This is called reproductive comparability.

Speciation

The process of creating new species. This occurs by splitting already existing species.

The first step of Speciation

One population becomes reproductively isolated from another population

The second step of Speciation

Reproductively isolated populations evolve separately from each other.

The third step of Speciation

Eventually reproductively isolated populations undergo enough divergent evolution that they can no longer interbreed, making them new species.

Divergent Evolution

The accumulation of differences between closely related populations within a species, sometimes leading to speciation.

Allopatric Speciation

Speciation that occurs in separate locations. This type of speciation occurs when populations are reproductively isolated because of geographic isolation.

Sympatric Speciation

Speciation that occurs in one location. This type of speciation occurs when populations are reproductively isolated but not physically separated. This can occur due to behavioral or temporal (time based) isolation.

Prezygotic Barrier

An obstacle to mating or to fertilization if mating occurs. Examples of this are Geographic, Behavioral, and Temporal isolation.

Postzygotic Barrier

Prevents the offspring of two different species from developing into viable, fertile adults.

Reduced Hybrid Viability

A type of postzygotic barrier. This occurs when two species are capable of producing offspring but that offspring has fails to develop properly into a healthy adult.

Reduced hybrid fertility

A type of postzygotic barrier. This occurs when two species are capable of producing healthy hybrids but those hybrids are sterile.

Hybrid Breakdown

Occurs when the first generation of hybrids is fertile, but subsequent generations are sterile.

Gradualism

The theory that speciation occurs slowly, with small changes accumulating over a long time period.

Evidence for Gradualism

The fossile record of the horse, which shows a large number of minor changes occuring over a long time.

Punctuated Equalibrium

The theory that speciation occurs suddenly, with populations remaining stable for long periods of time before suddenly undergoing abrupt and rapid change.

Evidence for Punctuated Equalibrium

There is a general lack of fossil records showing species undergoing minor changes, however this could be explained by the relatively rare and infrequent forming of fossils.

Ploidy

The number of copies of each chromosome in a cell.

Diploid

Two copies of each chromosome per cell

Haploid

One copy of each chromosome per cell

Polyploid

More than two copies of each chromosome per cell, this is a trait found in some plants.

The Three ways Variation Occurs during sexual reproduction

Crossing over, Random assortment of chromosomes, Random fertilization

Random fertizilation

One of the ways Variation occurs during sexual reproduction. This refers to the randomness of which sperm reaches the egg first. This basically m Evans that all sperms are slightly different.

Morphological concept of species

The classification of organisms into species based on shared physical characteristics.

Failures of the morphological concept of species

Two species that are very different may have similar physical characteristics, leading to them mistakenly being classified as the same species. There may be physical variation within a species (such as sexual dimorphism) that would be treated as separate species.

DNA Sequencing

A technique that looks at the sequence of the bases within a DNA molecule. Organisms of the same species have very similar genomes, meaning we can use this to determine whether organisms are of the same species. We can also use this to help determine how closely related two species are.

Genome

All of the genetic information in an organism.

SNPs (Single-Nucleotide Polymorphisms)

Minor differences in the genomes of organisms of the same species. These involve the replacement of a single nucleotide with another and create genetic variance/diversity in a species.

Genome Size

The amount of DNA in a haploid cell. Genomes of different species vary in size and sequence. Variation within a species is much lesser than variation between species.

Human Chromosomes

Humans have a Diploid Number of 46, that means we have two copies per cell of 23 unique chromosomes. Chromosomes 1-22 are autosomes (do not play a major role in sex determination).

Homologous Chromosomes

Each pair of human autosomes (chromosomes 1-22) are homologous, meaning they have the same gene sequence, loci (location), and chromosome length.

Locus (plural: loci)

A term used to refer to a chromosomes location.

Alleles

These are diffent variations of the same gene. Homologous chromosomes can have different alleles.

Human sex chromosomes

The 23rd pair of chromosomes. These contain the genes that play a major role in sex determination. Chromosomically typical females have xx and chromosomically typical males have xy. These are not homologous, the x chromosome is much larger than the y chromosome.

Chromosomes #12 & #13

The chrosomes we believe merged to form chromosome #2.

Clade

A group of species with a single common ancestor. Must include all species with said ancestors and no species without said ancestor.

Cladistics

A way to represent evolutionary relationships between species.

Root

The common ancestor shared by the entire tree in a cladogram

Node

A common ancestor shared by the 2+ lineages that branch off of it in a cladogram, represents speciation occuring

Terminal Branch

The end of the cladogram, these represent the extant (still living) species

Outgroup

The most distantly related extant species in a cladogram. The outgroup is often compared to other species.

Derived Characteristic

A trait that arose at a certain node and is shared among its descendents

Directional Selection

A type of natural selection where one extreme is selected for over another.

Stabilizing Selection

A type of natural selection where the middle is favored over the extremes.

Disruptive Selection

A type of natural selection where both extremes are selected for over the middle, this creates a bimodial distribution.

Autotrophic

Does not have to consume things in order to survive. Photosynthesis (photoautotrophic) is an example of this.

Heterotrophic

Has to consume things in order to survive.