exam 1 bio 2

analogy

(also, homoplasy) characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path

Reproductive isolation

(the ability to interbreed, of the two populations) can take place in a variety of ways. Note: zygote = fertilized egg.

Early beliefs about species leading to the development of evolution by natural selection:

- Contribution of fossils and field of paleontology Scientists determine the age of fossils and categorize them from all over the world to determine when the organisms lived relative to each other. The resulting fossil record tells the story of the past and shows the evolution of form over millions of years. For example, scientists have recovered highly detailed records showing the evolution of humans and horses. The whale flipper shares a similar morphology to bird and mammal appendages indicating that these species share a common ancestor.

Early beliefs about species leading to the development of evolution by natural selection:

- Jean Baptiste Lamarck proposed mechanism of how organisms evolved through time.Use or disuse •Inheritance of acquired characteristics. Long story short: physical changes in organisms during their lifetime—such as greater development of an organ or a part through increased use—could be transmitted to their offspring.

Charles Darwin

-Observed variation in species based on environmental conditions .Evolution by "natural selection" (the weaker die out) wrote On the Origin of Species decent with modification

Key points of natural selection

> natural selection only works on inherited traits >individuals do not evolve populations evolve >results from unequal reproductive success >evolution is not working towards a specific goal "perfect"organism + adaptations are specific to environment!

Polytomy

A branch with more than two lineages/species

Founder effect:

A small number of individuals colonizes a new location and their alleles become a major part of the isolated population. Such a colonization event can occur by natural dispersal or human-mediated transport.

Biological Species Concept- what is the primary condition that needs to be met to determine if individuals are separate species?

According to this definition, one species is distinguished from another when, in nature, it is not possible for mating between individuals from each species to produce fertile offspring. Members of the same species share both external and internal characteristics, which develop from their DNA. The closer relationship two organisms share, the more DNA they have in common >•Group of populations with potential for successful breeding in nature and able to create fertile offspring • Most commonly used today •Gene flow helps to "hold" a species together genetically • Reproductive isolation between species maintains separate species • Sometimes does not work= hybrids (offspring of 2 different species) New species arise from reproductive isolation between populations • Defined as separate species only after reproductive isolation mechanisms have developed

genetic drift

Allele frequencies randomly change from one generation to the next.

Basal Taxon:

An early and unbranched lineage

Bottleneck effect

An event kills a large amount of a population and only a small subset is left. Results in a loss of genetic diversity. Can be due to a natural disaster or anthropogenic events (ex. People overharvesting fish).

Anatomy and Embryology

Another type of evidence for evolution is the presence of structures in organisms that share the same basic form. For example, the bones in human, dog, bird, and whale appendages all share the same overall resulting from their origin in a common ancestor's appendages. Over time, evolution led to changes in the bones' shapes and sizes different species, but they have maintained the same overall layout. Scientists call these synonymous parts homologous structures.

3 domains of life

Bacteria, Archaea, Eukarya

allopatric speciation

Biologists group allopatric processes into two categories: dispersal and vicariance. Dispersal is when a few members of a species move to a new geographical area, and vicariance is when a natural situation arises to physically divide organisms.

Alfred Russel Wallace

British naturalist who developed a hypothesis of natural selection similar to Darwin's also decent with modification

Molecular Biology

DNA Fundamental divisions in life between the genetic code, DNA replication, and expression are reflected in major structural differences

descent with modification

Darwin and Wallace reasoned that offspring with inherited characteristics which allow them to best compete for limited resources will survive and have more offspring than those individuals with variations that are less able to compete. Because characteristics are inherited, these traits will be better represented in the next generation. This will lead to change in populations over generations in a process that Darwin called descent with modification. DNA's universality reflects evidence of a common ancestor for all of life. Adaptations accumulated in populations from changing environmental factors Created new species + increased biodiversity

How did travels on HMS beagle influence the development of Charles Darwin's ideas about evolution?

Darwin traveled around the world on H.M.S. Beagle, including stops in South America, Australia, and the southern tip of Africa. Wallace traveled to Brazil to collect insects in the Amazon rainforest and to the Malay Archipelago. Darwin's journey, like Wallace's later journeys to the Malay Archipelago, included stops at several island chains, the last being the Galápagos Islands west of Ecuador. On these islands, Darwin observed species of organisms on different islands that were clearly similar, yet had distinct differences. The species on the islands had a graded series of beak sizes and shapes with very small differences between the most similar. He observed that these finches closely resembled another finch species on the South American mainland. Darwin imagined that the island species might be species modified from one of the original mainland species. Upon further study, he realized that each finch's varied beaks helped the birds acquire a specific type of food. He postulated that ancestral species' beaks had adapted over time to equip the finches to acquire different food sources. Darwin called this mechanism natural selection. Natural selection, or "survival of the fittest," is the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits. This leads to evolutionary change.

Conditions for a population to be in equilibrium and what happens if conditions are not met?

Describes a population that is not evolving. There must be random mating, no mutations, no migration, no natural selection, and a large sample size. If the assumptions are not met for a gene, the population may evolve for that gene (the gene's allele frequencies may change).

Natural Selection "survival of the fittest"

Evolution by natural selection describes a mechanism for how species change over time: The more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits. This leads to evolutionary change. genetic variation in population, not all reproduce in pop.

organisms that share similar environments

For example, species of unrelated animals, such as the arctic fox and ptarmigan, living in the arctic region have been selected for seasonal white phenotypes during winter to blend with the snow and. These similarities occur not because of common ancestry, but because of similar selection pressures—the benefits of predators not seeing them.

speciation

For speciation to occur, two new populations must form from one original population and they must evolve in such a way that it becomes impossible for individuals from the two new populations to interbreed.

Speciation

Formation of new species

Main sources of evidence for evolution by natural selection.

Fossils, anatomy and embryology, organisms that share similar environments,embryology,biogeography,molecular biology.

Stabilizing Selection:

If natural selection favors an average phenotype, selecting against extreme variation, the population will undergo stabilizing selection.

where does polyploidy most commonly take place

It takes place most commonly in plants. Scientists have discovered more than half of all plant species studied relate back to a species evolved through polyploidy

What mechanisms can cause change in a population?

Natural Selection, Genetic Drift, Mutations, Gene Flow.

which mechanism usually leads to adaptive evolution?

Natural selection is the only evolutionary mechanism that consistently leads to adaptive evolution.

limits of natural selection

New alleles don't appear when needed Ancestral structures are adapted to new situations. One characteristic may be an adaptation in one situation but a disadvantage in another. Chance events can alter frequencies in population Environment can change.

Polyploid Speciation-

Polyploidy is a condition in which a cell or organism has an extra set, or sets, of chromosomes. Polyploidy results from an error in meiosis in which all of the chromosomes move into one cell instead of separating. The other form of polyploidy occurs when individuals of two different species reproduce to form a viable offspring that we call an allopolyploid.

what makes polyploid speciation different from most other mechanisms of speciation? What group of organisms is this most common in?

Scientists have identified two main types of polyploidy that can lead to reproductive isolation of an individual in the polyploidy state. Reproductive isolation is the inability to interbreed. In some cases, a polyploid individual will have two or more complete sets of chromosomes from its own species in a condition that we call. The prefix "auto-" means "self," so the term means multiple chromosomes from one's own species

intersexual selection

Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.

Directional Selection:

Selects for phenotypes at one end of the spectrum of existing variation and against the other end; genetic variation toward new, fit phenotype.

Diversifying Selection:

Sometimes two or more distinct phenotypes can each have their advantages for natural selection, while the intermediate phenotypes are selected against.

habitat differentiation

Sympatric speciation scheme in which mutations in a population allow individuals to exploit different conditions within the same environment.

Biogeography

The geographic distribution of organisms on the planet follows patterns that we can explain best by evolution in conjunction with tectonic plate movement over geological time. Broad groups that evolved before the supercontinent Pangaea broke up (about 200 million years ago) are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, such as the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana.

Evolution

The gradual change in a species over time

Gene Flow:

The movement of alleles among populations; small groups of one population moving through another. Gametes can also travel via the environment.

Mutations:

The raw material of natural selection. A change in DNA sequences that creates new alleles. Can be positive, negative, or neutral.

Microevolution

The theory also connects population change over time, especially over a short period.

What is a phylogenetic tree? What does it represent?

They show the evolutionary history of a species. "Trees of Life" can represent relationships ranging from the entire history of life on earth, down to individuals in a population. Hypothesis of the past.

sympatric speciation

We call the process of speciation within the same space.The prefix "sym" means same, so "sympatric" means "same homeland" in contrast to "allopatric" meaning "other homeland." -can begin with a serious chromosomal error during cell division. In a normal cell division event chromosomes replicate, pair up, and then separate so that each new cell has the same number of chromosomes. However, sometimes the pairs separate and the end cell product has too many or too few individual chromosomes in a condition that we call aneuploidy

Why do others not result in adaptive evolution?

While natural selection selects the fittest individuals and often results in a more fit population overall, other forces of evolution, including genetic drift and gene flow, often do the opposite by introducing deleterious alleles to the population's gene pool.

punctuated equilibrium model

a new species undergoes changes quickly from the parent species, and then remains largely unchanged for long periods of time afterward.

Postzygotic

barrier occurs after zygote formation. This includes organisms that don't survive the embryonic stage and those that are born sterile. Postzygotic barriers can prevent reproduction. Hybrid individuals in many cases cannot form normally in the womb and simply do not survive past the embryonic stages. We call this hybrid inviability because the hybrid organisms simply are not viable. In another postzygotic situation, reproduction leads to hybrid birth and growth that is sterile. Therefore, the organisms are unable to reproduce offspring of their own. We call this hybrid sterility.

Reasons evolution is considered a unifying theory of biology.

biodiversity,relatioship between living organisms,why/how organisms are wellsuited to so many different

structures of analogy

characteristics occur due to environmental conditions, not close evolutionary relationship Similar function Butterfly and bird wings

intrasexual selection

competition among individuals of one sex (often males) for mates of the opposite sex

shared ancestral characteristics

describes a characteristic on a phylogenetic tree that all organisms on the tree share

shared derived characteristic

describes a characteristic on a phylogenetic tree that only a certain clade of organisms share

phylogeny

evolutionary history and relationship of an organism or group of organisms

shared derived characteristics

evolutionary novelty that is unique to a certain clade Trait that derives at some point but does not include all of the ancestors in the tree. It is unique to a particular clade.

structures of homology

features overlapping both morphologically and genetically Similar origin

outgroup

group of organisms that serves as a reference group in determining the evolutionary relationships of the ingroup.

adaptations

heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment

Rooted tree

includes branch to represent the most recent common ancestor of all taxa in the tree.

Convergent Evolution:

independent evolution of similar features in different lineages; ex. Slim bodies for streamlining in aquatic species (otters, fish, etc.)

Prezygotic

is a mechanism that blocks reproduction from taking place. This includes barriers that prevent fertilization when organisms attempt reproduction. (Some types of prezygotic barriers prevent reproduction entirely. Many organisms only reproduce at certain times of the year, often just annually.) Other prezygotic barriers work when differences in their gamete cells (eggs and sperm) prevent fertilization from taking place. We call this a gametic barrier.

ingroup

is the set of taxa which is hypothesized to be more closely related to each other, taxa in the ingroup are sister groups of each other

Evolutionary Lineage

line of descent of a taxon from its ancestral taxon

hybrid

offspring of two closely related individuals, not of the same species

Clade/Monophyletic Group:

organisms that share a common ancestor, stem from a single point.

shared ancestral characteristics

originates in an ancestor of the taxon Characteristics found in group's ancestor and it is present in all of the organisms within the taxon or clade

Hardy-Weinberg equilibrium allele frequency

p+q=1

Hardy-Weinberg equilibrium genotype frequency

p^2 + 2pq + q^2 = 1

Homologous Structures

parallel structures in diverse organisms that have a common ancestor

Vestigial Structures

physical structure present in an organism but that has no apparent function and appears to be from a functional structure in a distant ancestor

Evolution and Populations

population is the unit that evolves

fossils

provide solid evidence that organisms from the past are not the same as those today, and fossils show a progression of evolution.

branch points

represents divergence of two evolutionary lineages from common ancestor.

Natural selection:

reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change

Analogy

similar characteristics occur due to environmental conditions.

homology

similar due to ancestors

Homology

similarity of the structure, physiology, or development of different species of organisms based upon their descent from a common evolutionary ancestor.

gradual speciation model

species diverge gradually over time in small steps.

embryology

the study of the anatomy of an organism's development to its adult form, also provides evidence of relatedness between now widely divergent groups of organisms. Mutational tweaking in the embryo can have such magnified consequences in the adult that tends to conserve embryo formation.

sister taxa

two species that share an immediate common ancestor that's only shared between them

how quickly speciation occurs

we can observe two current patterns: gradual speciation model and punctuated equilibrium model.