AP Biology Unit One

null hypothesis

- A prediction that there is no difference between groups or conditions
- ex. "wealth has no effect on happiness"

active hypothesis

- declares that there is some correlation but does not specify what it is
- ex. "wealth has some effect on happiness"

prediction

- hypothesis where you make a specific claim
- ex. "wealth increases happiness"

independent variable

The experimental factor that is manipulated; the variable whose effect is being studied.

dependent variable

The outcome factor; the variable that may change in response to manipulations of the independent variable. the data; the output.

control group

In an experiment, the group that is not exposed to the treatment; contrasts with the experimental group and serves as a comparison for evaluating the effect of the treatment.

Controlled variables

All those things that must be kept the same during the investigation to produce a valid, fair test.

treatment group

- the participants in an experiment who are exposed to the level of the independent variable that involves a medication, therapy, or intervention
- same as experimental group

properties of life

1. Order
2. Reproduce
3. Growth & Development
4. Energy consumption
5. Responds to Environment:
6. Regulation / Homeostasis
7. Evolutionary Adaptation

DNA

code for making proteins

proteins

- what gives us our traits (ex. height, weight, etc)
- things like adrenaline and melatonin

homozygous

An organism that has two identical alleles for a trait

Heterozygous

An organism that has two different alleles for a trait

phenotype

- physical expression of an organism's genotype
- our physical appearances; what we look like
- ex. brown eyes, black hair, etc

allele

- An alternative form of a gene
- what forms genes
- we get one from each parent for each trait

gene

- segment of DNA
- codes for a protein
- determines physical characteristics and other aspects of who we are

mutations

- a random error in gene replication that leads to a change

recessive

- allele that is only physically expressive if an individual is homozygous for it

genotype

- combination of alleles an individual inherits for a trait

dominant

- allele that is always expressed in the phenotype if an individual inherits it

heterozygous

the condition of inheriting two different alleles for a trait

what is a carrier?

heterozygous genotype that carries recessive trait but doesn't express it

population

group of organisms belonging to the same species, living in the same place, at the same time

species

- a group of organisms that can interbreed to produce viable, fertile offspring
- different species are reproductively isolated from each other

viable

able to survive in natural environment

What is the main thing evolution is based on?

reproduction! evolution is all about who reproduces and who doesn't and how that impacts future generations of offspring. Every type of evolution boils down to reproduction.

evolution

change in the heritable characteristics of biological populations over successive generations. a change in the allele frequencies of a population

fertile

able to reproduce

principles of natural selection

1. Individuals in a certain species vary from generation to generation
2. Some of the variations are determined by the genetic makeup of the species
3. More individuals are produced than will survive
4. Some genes allow for better survival of an animal

(viariation, overproduction of offspring, differential reproductive success)

variation

- all individuals in populations have different traits/characteristics
- most of these variations are genetically determined and can be inherited by offspring (passed down by parents)
- mutations in DNA are the only source of completely new genetic variations in a population
- there are other mechanisms, though, in which new (to the population) traits can arise

what is the only source of completely new genetic variations within a population?

mutation

Overproduction of offspring

- a population can produce far more offspring than the environment can support
- this results in competition among offspring for available resources, so they start to compete for things like food and shelter
- only the most fit survive

differential reproductive success

- the tendency of some individuals to have greater reproductive success than other individuals in a population
- these traits enable them to better compete for resources
- ex. rabbits who run slower are eaten by foxes, and their traits are, therefore, not passed down

survival of the fittest

- those who are killed because they have traits that do not promote their success in an environment will die before they can reproduce and their traits won't be passed down
- ex. a green lizard in the desert. birds see it from above, and eat it while it is young. it was too young to reproduce, so it made no green lizard babies

adaptation

inherited characteristic that increases an organism's chance of survival in its environment

fitness

- Ability of an organism to survive and reproduce in its environment
- reproductive success of offspring
- the most fit individuals have the most viable offspring
- a fit organism is able to survive and make babies that will survive

natural selection

- A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
- causes populations to change
- differences in reproductive success cause adaptations to become more and more common in a population over a long period of time
- ergo, natural selection is the process by which certain, favorable, inherited traits become more common in a population

how do we know when a population is evolving?

when it is changing!

what is happening to allele frequencies if a phenotype is becoming more common in a population?

the allele frequencies of those alleles are increasing

what happens to alleles during evolution?

the frequencies of alleles for certain traits changes in a population

two ways to say a population has evolved

1. the characteristics of the population have changed over time
2. the allele frequencies have changed over time

do populations choose to change?

no!!!! they do not try to change-- they have a trait that is helpful in the environment and they are able to reproduce OR they have a trait that disadvantages them and they are not able to reproduce

do individuals within populations evolve?

NOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!! only populations can evolve, not individuals. evolution occurs alongside reproduction

how is extinction possible?

Extinction is possible if environmental conditions change faster than a species can adapt to those changes

how long does evolution take?

a loonggg time. think millions of years

microevolution

Change in allele frequencies in a population over generations.

Macroevolution

Evolutionary change above the species level; the formation of new species

bottleneck effect

- a reduction in the genetic diversity of a population caused by a reduction in its size
- when most of the species dies out due to change (ex. natural disaster such as hurricane) and the future of the species is based on the alleles of those that remain.
- produces less fit populations and less variety, so there are less mutations that could protect the species if there is future disaster

sexual selection

- A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
- animals mate with the prettiest animals because they may have physical characteristics that display better ability in child rearing or may produce happy neurotransmitters in the animals' brain
- ex the prettiest male peacocks are sexually selected for even though their giant, colorful feathers may not be advantageous in their natural environments

founder effect

- genetic drift that occurs after a small number of individuals colonize a new area
- small population from mainland goes to island and the DNA of all future generations on the island is derived from the small population of founders that came there.
- less genetic diversity.

gene flow

- Movement of alleles into or out of a population due to the migration of individuals to or from the population
- people from two different populations will get together and produce offspring that shares characteristics from both populations
- ongoing process. constantly occuring
- think about the "melting pot" that is the US
- more genetic variation
- based on immigration and emigration
- traits in a population shift based on who is coming in or leaving the population

genetic drift

- A change in the allele frequency of a population as a result of chance events rather than natural selection.
- encompasses bottleneck effect and founder effect because they are both totally chance
- founder effect is chance because settlers don't go to a new place with the desire to change the population. the population just changes because they are there

what does it mean if alleles change in frequency not because of natural selection?

the changing allele frequency is not dependent on fitness

sexual dimorphism

- distinct different in size or appearance between the sexes of a species
- key component of sexual selection because these traits often aid in competition or are selected by the opposite sex to pass onto offspring
- ex. male birds of prey often have beautiful coloring, but the females are rather plain. female praying mantasis are much bigger than their male counterpart

why does sexual selection occur?

- unique colorful traits may trigger dopamine production
- demonstrate the ability of the sex to care for offspring
- shows that the animal would be a good mate

how does the bottleneck effect impact populations?

it leaves them very vulnerable. there is less genetic diversity, and we need genetic diversity to deal with changing environments. if disaster were to strike, the population may not survive because they would be unable to adapt successfully due to lack of genetic diversity

what is the difference between speciation and macro evolution?

there is none!

speciation

- Formation of new species through evolutionary processes over time
- same as macroevolution, just another word for it
- the creation of new species
- ex monkeys--> homosapiens

what is needed for macroevolution to occur?

microevolution

if two animals look the same, are they from the same species?

not necessarily! different species may be similar in appearance, but appearance is not what determines a species. if these similar looking organisms cannot interbreed and successfully produce viable and fertile offspring, they are different species

two requirements for speciation

1. populations of the same species become isolated from one another
2. populations must genetically diverge

why is a requirement for speciation that populations of the same species must become isolated from each other?

- there must be no gene flow between them (no immigration or emigration) because then evolution would be affected
- may be geographically split (allopatric speciation) or split within the same area (sympatric speciation)
- the species may have to divide resources like food, water, location, etc to avoid competition with other organisms
- then different things in the area (ex. soil, trees, plants) may cause some traits to be favorable to those in each part of the region which can cause genetic changes and mutations that eventually lead to the formation of new species

why must populations genetically diverge for speciation to occur?

- when they are split, populations have different selective pressures that cause them to undergo microevolution and accumulate genetic differences
- eventually they develop barriers to reproduction and are too different to reproduce
- once the populations are isolated/separated and they undergo various forms of microevolution, their genes will accumulate differences, and since they are isolated they will not be able to share those genes with other populations. this means that they will continue to reproduce and mutate until the two populations are too different to interbreed

what is required of microevolution for speciation to occur?

microevolution must lead to the formation of one or more reproductive barriers
- traits must evolve that prevent production of viable, fertile hybrid offspring if the groups are brought back together

what are the main types of reproductive barriers?

prezygotic and postzygotic barriers

zygote

fertilized egg

prezygotic barriers

- mechanisms that prevent mating from occurring
- geographic isolation
- temporal isolation
- behavioral isolation
- mechanical isolation

postzygotic barriers

- mechanisms that prevent formation of viable, fertile offspring after mating has occurred
- basically when mating could happen, but a viable, fertile offspring could not be achieved
- ex. a horse and a donkey can mate and produce a mule, but the mule is unable to reproduce
- gametic isolation
- hybrid inviability
- hybrid infertility
- low hybrid fitness

geographic isolation

geographic separation prevents mating

behavioral isolation

- mating signals and behaviors differ between species which prevents mating
- ex. different songs and mating rituals. other species may not recognize these signals and therefore choose not to mate with them

temporal isolation

When two species breed at different times of day, season, or years.

mechanical isolation

- mating is attempted, but morphological differences prevent its successful completion
- body/reproductive organ shapes are incompatible

gametic isolation

- gametes (sperm and egg) can't combine
- some reasons may be differing numbers of chromosomes or the egg and sperm cannot reach each other

gametes

reproductive cells

hybrid inviability

- fertilized egg cannot progress past an early embryo.
- the hybrid does not survive.
- spontaneous abortions or ends in stillbirth

hybrid infertility

- viable hybrid offspring cannot reproduce
- hybrid is sterile
- ex. mules

low hybrid fitness

- hybrid is unlikely to survive AND reproduce
- ex. ligers or grolar bears
- the hybrids likely have traits from both parents that aren't great for the middle ground environment they inhabit between the species
- the hybrids do not have the best of the parent's traits

can populations adapt out of need?

no!!! they adapt with changes in allele frequencies and mutations over many generations caused by reproductive and selective pressures

can we get a new species by mating two other species

NO

when can we say if speciation occurred?

if the two species can't make babies or if their babies can't make babies

phylogeny

- the evolutionary history of a species or group of species
- an evolutionary "family tree" bsed on traits that are unique to and/or shared by a group of organisms and their common ancestor

how are phylogenies determined?

- The fossil record
- Morphological, homological, and molecular similarities

what are prezygotic and post zygotic barriers examples of?

reproductive isolation

homology

similarity resulting from common ancestry

morphology

refers to body structures (shape)

molecular

refers to DNA or protein structures/sequences. phylogenic trees compare the order of DNA nucleotides among different species to determine common ancestory and traits

what demonstrates a more recent shared ancestor?

- a similar order of A, T, G, and C, the smaller, molecular building blocks of DNA
- also the order of the amino acids

ancestoral/homologous traits

traits shared by a group of organisms and their common ancestor

derived traits

- newly evolved features, such as feathers, that do not appear in the fossils of common ancestors
- traits that a group shares that are not found in the common ancestor
- ex all mammals have mammory glands (ancestoral trait), but only primates have opposable thumbs (derived trait)
- derived traits can help us understand how groups of animals are more closely related to each other than to other groups also derived from the same common ancestor

what type of evidence is more accurate when constructing phylogenetic trees?

Molecular evidence because comparing the sequences of as many genes as possible increases the reliability

what is the main difference in phylogenetic trees v cladograms?

phylogenetic trees can only be made when you are given a timeline. the lines dictate time, while in cladograms time is not needed and you simply know that the most recent species and oldest species derived from a common ancestor are at either ends

what does each divergent point on a cladogram/phylogenetic tree represent?

a speciation event. the common ancestor underwent speciation and new species were formed

picture of my notes on cladograms and how to draw them because i am a # visual learner

what conditions must be met for hardy weinberg equilibrium to be true?

1. no selection
2. no mutation
3. no gene flow/migration
4. large population (more genetic diversity)
5. random mating (no selection)

what does it mean for a population to be in hardy weinberg equilibrium?

everything is balanced. from one generation to the next, alleles remain constant and common within the population

Two Hardy-Weinberg Equations

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

percents are written in decimal form (60%=.6)

p+q=1

- p= frequency of dominant allele
- q= frequency of recessive allele
- allele frequency equation

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

- genotype and phenotype frequency equation
- p^2 is the frequency of homozygous dominant genotypes
- q^2 is the frequency of homozygous recessive genotypes
- 2pq is the frequency of heterozygous genotype

in a population of 120 people, 30 have the dominant phenotype of being polydactyl. what part of the hardy weinberg equilibriums does this tell us?

dominant phenotype = p^2 + 2pq, so p^2 + 2pq= 30/120. from here, it would be easiest just to solve for q^2, then q, then p, then p^2, then 2pq

in a population of 120 people, 90 people have the recessive phenotype of only having five fingers on both hands. what is the frequency of the recessive allele?

q^2=90/120
so (9/12)^.5 = q