Biology 2 Exam 1

Allopatric vs sympatric speciation

* Allopatric: New species arise from reproductive isolation (No gene flow); Often results from a geographic barrier * Sympatric: New species arise in the same location as original pop. - Habitat Differentiation = pops. separate b/c of different uses of habitat - Sexual Selection - Polyploid Speciation Ex. 600 species of African Cichlids in Lake Victoria

Exaptations

* Definition: structures that evolve in 1 context but become co-opted for a diff. function * Represents a limit of natural selection b/c structures do not evolve in anticipation of future use; natural selection can only improve a structure in the context of its current utility

What makes Polyploid Speciation different from most other mechanisms of speciation?

* Occurs when there is an error in meiosis which creates a new organism w/ double the chromosome # * Most common in plants - Plants can self-fertilize, preventing the altered chromosome # from disrupting reproduction, so it becomes isolated from rest of pop. b/c of altered chromosome #

What were the major schools of thought on species, diversity, & change over time prior to Darwin?

* Pre-1700s: organisms were "perfect" & "permanent"; began w/ Aristotle * Carolus Linnaeus: developed binomial naming system for classifying biodiversity * Mid-1700s: Field of paleontology is born, fossil record * Early 1800s: Jean Baptiste Lamarck (not supported by genetics) - 1) use or disuse = organisms change traits by using/not using certain body parts, 2) inheritance of acquired characteristics = parents pass changed to offspring

What happens if conditions are not met for Hardy-Weinberg?

* we expect the population is evolving at a particular locus

How many mass extinctions?

- 5 - Cretaceous mass extinction is most well known - 6th mass extinction? Mammals & birds are suffering the most

What is a phylogenetic tree? What does it represent?

- A diagram that represents evolutionary relationships among organisms; hypothesis, not facts - Allows us to predict features of an ancestor from features of its descendants

Limitations of Biological Species Concept

- Cannot be applied to fossils or asexual organisms - Emphasizes absence of gene flow

Genetic Drift

- Causes allele frequencies to change randomly (Non-adaptive evolution) - More influential in small pops. - Often causes a decrease in genetic diversity

Mutations

- Change in DNA sequences * Errors in creating DNA * Damage to DNA strand - May be negative, neutral, or beneficial

What is descent with modification?

- Current species came from a succession of ancestors - Descendants accumulated adaptations as a result of changing environmental factors - Resulted in new species and increased diversity

Limitations of the Fossil record

- Few organisms have fossilized, & even fewer of the fossils that did form have been discovered - Biased in favor of species that: * existed for a long time * were abundant & widespread * had hard parts, such as shells or skeletons

Biological Species Concept

- Group of pops. w/ potential for successful breeding in nature & able to create FERTILE OFFSPRING

Protocells are believed to represent the initial form of life because they exhibit which of the following living properties?

- Growth - Metabolism - Reproduction

Types of post-zygotic reproductive barriers

- If zygote forms, barriers can prevent continued hybridization (Reduced hybrid viability) 1) Reduced Hybrid Fertility: Hybrid is viable but sterile (Ex. Horse + Male Donkey = Mule) 2) Hybrid Breakdown: First generation offspring are viable & fertile, but second generation has reduced viability

Adaptations

- Inheritable characteristics - Gives organisms better chance of survival & reproductive success through interactions w/ environment

What evidence supports Endosymbiosis?

- Inner membranes of both organelles are similar to plasma membranes of living bacteria - DNA structure & cell division are similar to bacteria - Both organelles transcribe & translate their own DNA - Ribosomes are more similar to bacterial than to eukaryotic ribosomes

Cambrian Explosion

- Large # of animal fossils suggests period of high rates of diversification - 1st evidence of predator-prey interactions * New defense adaptations appeared & large-bodied predators w/ claws

Gene Flow

- Movement of alleles from one population to another - If high rates of gene flow is occurring btwn pops, reduces genetic variation among pops. over time (all individual pops. have similar gene pool) *Barriers to dispersal can limit gene flow

When Charles Darwin published the Origin of Species, he provided evidence for which of the following concepts related to evolution?

- descent with modification as a process for speciation - Natural selection as a mechanism for change

We can assume that the locus that causes phenylketonuria (PKU) is in Hardy-Weinberg equilibrium given that the following conditions are met... 1.The PKU gene mutation rate is low 2.Mate selection is random with respect to whether or not an individual is a carrier for the PKU allele 3.Natural selection can only act on rare homozygous individuals who do not follow dietary restrictions 4.The population is large 5.Migration has no effect, as many other populations have similar allele frequencies Previous genetic studies have shown the occurrence of PKU, a homozygous recessive condition, is one per 10,000 births. Based on this information calculate the following (answers should be rounded to 2 places after decimal as needed): The frequency of q (i.e the recessive allele)...? The frequency of the p (i.e. the dominant allele)...? The frequency of carriers of the PKU allele (i.e. heterozygous condition)...? If 100 years later, research showed the frequency of q was 0.2, does this show the population was still in Hardy-Weinberg equilibrium (enter Yes or No)?

- frequency of q: .01 - frequency of p: .99 - frequency of carriers of the PKU allele: .02 - Was the pop. in equilibrium? No

Adaptive radiation can occur because of which of the following factors?

- mass extinctions - colonization of a new region - evolutionary innovation - vacant ecological niches

Fossil records are important for understanding change in living organisms, however, there are multiple limitations including ________________.

- not all fossils have been found - evolutionary trends in fossils may change when new fossils are found - some organisms do not create fossils - fossil records are biased towards certain types of species

What are the 2 Hardy-Weinberg equations?

- p+q=1 (Freq. of alleles) - p^2 + 2pq +q^2 = 1 (Freq. of genotypes)

How does fossil record help us understand evolution?

- reveals changes in the history of life on Earth - Order of fossils in rock strata tells us the order in which they were formed - reveals evolutionary trends in some lineages

Adaptive Radiation

- the rapid evolution of diversely adapted species from a common ancestor - May follow: mass extinctions, the evolution of novel characteristics, the colonization of new regions

Orthologous genes

- widespread & extend across many widely varied species - assume nucleotide substitutions are proportional to time since they last shared a common ancestor

What were the 2 big observations Darwin made while on the HMS Beagle?

1) Animals/plants had characteristics specific to the environment they inhabited 2) Organisms on islands were similar but different from organisms on mainland

3 domains of life

1) Bacteria 2) Archaea 3) Eukarya

How does natural selection occur?

1) Sexual Dimorphism = males usually "showier" of sexes or engage in competition for females (Characteristics may be disadvantage) 2) Intrasexual selection = competition among individuals of 1 sex for mates of the opposite sex 3) Intersexual selection = individuals of 1 sex are choosy in selecting their mates

Types of pre-zygotic reproductive barriers

1) Temporal Isolation - Mating occurs during diff. seasons/diff. times of day 2) Habitat Isolation 3) Behavioral Isolation (Birds of Paradise) 4) Mechanical Isolation (sex organs don't fit together) 5) Gametic Isolation (Ex. Starfish has 36 chromosomes & a dolphin has 44, so they cannot mate)

Sickle-Cell Disease

1) What causes it?: The change in amino acid sequence causes hemoglobin molecules to crystallize when oxygen levels in blood are low. As a result, red blood cells sickle & get stuck in small blood vessels 2) How does it interact w/ malaria infection?: people w/ sickle-cell are more resistant to malaria b/c the protists can't enter the sickle-cell shape; shows how mutations can be beneficial in a specific environment 3) Why do heterozygotes have an advantage?: co-dominant alleles, both types of blood cells.. Heterozygotes have decreased symptoms of malaria & decreased symptoms of sickle-cell disease, so higher survival

Adaptive evolution

1) Which mechanism usually leads to adaptive evolution?: Natural selection 2) Why do others not result in adaptive evolution? B/c of random processes

4 stages necessary for simple cells to develop on Earth

1. Abiotic synthesis of small organic molecules 2. Joining of these small molecules into macromolecules 3. Packaging of molecules into protocells 4. Origin of self-replicating molecules

Types of Macroevolution

1. Adaptive Radiation: Ex. The disappearance of dinosaurs opened ecological niches, allowing for the expansion of mammals in diversity & size 2. Mass Extinctions: can change the types of organisms found in ecological communities 3. Plate Tectonics & Continental drift: Formation of Pangea had many effects including a deepening of ocean basins, a reduction in shallow-water habitat, and a colder & drier climate inland... Continental drift impacts organisms b/c they must adapt, move, or risk extinction as the climate changes in response to continents moving toward or away from the equator & separation of landmasses can lead to allopatric speciation

A small subset of a population of bats on the mainland colonized an island. Over time, gene flow between the island and the mainland decreased due to the long distance between the two locations. The island bats began accumulating adaptations different than the original population on the mainland. Scientists studying the two populations decided the island bat were different enough to suggest the island population be designated a different species. 1. If this is true, this would represent which type of speciation? 2. Based on the Biological Species Concept, what condition needs to be met to designate them different species?

1. Allopatric speciation 2. if individuals from the 2 populations came together, they could not successfully produce viable offspring

Choose the type of selection occurring in each of the populations below 1. A population of rabbits have the highest reproductive rates by individuals with the darkest and lightest fur colors. 2. A population of beetles have the highest reproductive rate by individuals with the darkest carapace color due to the introduction of a new tree with darker colored bark. 3. Stable climate in a forest results in the most common phenotype of bird species producing the most offspring for the past 10 generations 4. Female cichlids prefer males with blue colorings, leading to a greater number of blue individuals in each generation

1. Disruptive selection 2. Directional selection 3. Stabilizing selection 4. Sexual selection

_________________ are structures that evolve in one context but become co-opted for a different function. This represents which limit of natural selection?

1. Exaptations 2. Natural selection is limited by historical constraints

Types of Microevolution

1. Natural selection 2. Mutations 3. Genetic drift 4. Gene flow

What are the conditions for a population to be in equilibrium according to Hardy-Weinberg?

1. No mutations 2. Random mating 3. No natural selection 4. Extremely large population size 5. No gene flow

Key points of natural selection

1. Results from unequal reproductive success 2. Individuals do not evolve, populations evolve 3. Natural selection only works on inheritable traits 4. Evolution is not working towards a specific goal or "perfect" organisms

Limits of natural selection

1. Selection can only act on existing variation in a population 2. Evolution is limited by historical constraints 3. Adaptations are usually compromises 4. Natural selection interacts with chance/random events and the environment

Choose which of the following examples that best explain each of the following limits of natural selection. 1. Hunting has decreased the population size of elephant seals, decreasing potential for natural selection due to extremely low genetic diversity. 2. Penguins have modified wings to use for swimming. 3. The male peacock has bright feathers to attract females, however, these characteristics make them more visible to predators 4. Introduced species can change which characteristics are advantageous for a population

1. Selection can only act on existing variation in a population. 2. Evolution is limited by historical constraints. 3. Adaptations are compromises. 4. Natural selection interacts with chance/random events and the environment.

Shared ancestral vs Shared derived characteristics

Ancestral = character originated in an ancestor of the taxon Derived = evolutionary novelty unique to a particular clade

Colonization of Land

Arthropods & tetrapods forming

Why is evolution considered a unifying theory of biology?

B/c it explains biodiversity, the relationship btwn living organisms, & why/how organisms are well-suited to so many different environments

Evolution

Change over time

Monophyletic Group

Consists of ancestor species + all descendants (clade)

Paraphyletic Group

Consists of ancestral species + some descendants

Homeotic Genes

Determine such basic features as where wings and legs will develop on a bird or how a flower's parts are arranged

Ediacaran Time Period

Early Multicellular Organisms

What does Endosymbiosis say about evolution of eukaryotic cells?

Eukaryotes originated by endosymbiosis when a prokaryotic cell engulfed a small cell that would evolve into a mitochondrion

Convergent Evolution

Evolution toward similar characteristics in unrelated species

T/F: The fossil records shows the rate of speciation is the same for all taxa.

False

Bottleneck effect

Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population

Founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population

Clade

Group of species w/ an ancestral species and all its descendants

Homology vs. Analogy

Homology = similarity due to shared ancestry Analogy = similarity due to convergent evolution

Horizontal gene transfer - how does it occur?

Occurs by: - Exchange of transposable elements & plasmids - Viral infection - Possibly fusion of organisms

Speciation

Process of 1 species separating into 2 or more species

Differences btwn punctuated model & gradual model of speciation

Punctuated: periods of stability followed by rapid change Gradual: gradual but consistent change over time

Vestigial Structures

Remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species

Homology

Similarity resulting from common ancestry

Outgroup

Species or group of species that is closely related to ingroup, but diverged before the ingroup

Which of the following is a reason evolution is considered a unifying theory of biology?

Supported by data from a large group of disciplines, including biogeography, comparative anatomy, and molecular biology

What is natural selection?

The idea that the fittest survive and pass along their traits to their offspring * unequal reproduction is essential

T/F: Extinction is a natural process and has occurred throughout geological time.

True

The influence of sexual selection on development of characteristics to improve potential for mating highlights the essential process of __________________ for natural selection to cause change in populations.

Unequal reproduction

Endosymbiont

a cell that lives within a host cell

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped make possible the evolution of a tetrapod limb. This type of change represents which of the following?

a change in a developmental gene or in its regulation that altered the spatial organization of body parts

What is a scientific theory?

a well-tested concept that explains a wide range of observations * starts off as a hypothesis

Heterochromy

an evolutionary change in the rate or timing of developmental events

Systematics

classifies organisms and determines their evolutionary relationships

Polyphyletic group

distantly related species but does not include most recent common ancestor

Disruptive selection

favors individuals at both extremes of the phenotypic range * would favor white and brown mice on the spectrum

Directional selection

favors individuals at one extreme end of the phenotypic range * would favor all brown mice

Stabilizing Selection

favors intermediate variants and acts against extreme phenotypes * would favor middle mouse, which is a mixture of the brown & white mice

Which of the following steps has not yet been accomplished by scientists studying the origin of life?

formation of protocells using DNA to direct the polymerization of amino acids

Sister Taxa

groups that share an immediate common ancestor that is not shared by any other group

Rooted tree

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

Protocells

may have formed from fluid-filled vesicles with a membrane-like structure

The only mechanism for microevolution consistently leading to adaptive evolution in a population is .....

natural selection

Hybrid

offspring of 2 species mating

Long-term trends over geological history in speciation and extinction rates can be partially explained by...

plate tectonics and continental drift

Habitat differentiation

pops. separate b/c of diff. uses of habitat

The oldest fossils identified so far, the stromatolites, represent which type of cell?

prokaryotes

The endosymbiosis theory states the origin of eukaryotic cells began when _______________.

prokaryotic cell consumed a smaller cell

Protocells: what 2 key properties of life are they able to do?

replication & metabolism

Branch points

represents the divergence of two evolutionary lineages from a common ancestor

Paralogous genes

results from gene duplication - found in more than 1 copy in the genome - diverge within the species that carries them & often evolve new functions

Homologous structures

similar structures that related species have inherited from a common ancestor even if function is different

ingroup

species being studied & compared

The field of paleontology changed naturalist's views of biodiversity by showing...

species were neither perfect or permanent

Phylogeny

the evolutionary history of a species or group of related species