Exam 2 Study Guide Anthro 101

What are Chromosomes?

Chromosomes are genetic information that is arranged as rows of genes. Genes are segments of DNA that perform specific functions; Chromosomes are tiny structures in cells that carry our genetic information. They are made of DNA and help pass traits from parents to their children. Humans have 46 chromosomes, arranged in 23 pairs.

Autosome

governs all physical characteristics except sex determination

Sex chromosome

determines biological sex; X and Y chromosomes

-Mammal females have two X chromosomes

-Mammal males have one X and one Y chromosome

Haploid

chromosomes are single; half the genetic information

-Gametes are haploid

-Human gametes have 23 chromosomes

Diploid

chromosomes are arranged in pairs

-Humans have 46 chromosomes arranged in 23 pairs

-Somatic cells are diploid

Mitosis

-Ordinary cell division of somatic cells

-Produces two daughter cells

-Contains homologous pairs of chromosomes (but chromosomes only form prior to division). Having a pair of chromosomes is called “diploid”

Meiosis

-Cell division, which produces gametes

-Gametes are haploid (in contrast to diploid), containing half of an individual’s genetic material

-Recombination

variation

Mutation and recombination are sources of variation

Mendelian genetics and Mendel’s Principles

-Each parent contributes particles to offspring (alleles)

-Each parent contributes one gene form or another (meiosis produces haploid gametes)

Know how to calculate Mendelian inheritance using a Punnett square and report genotype and phenotype frequencies

Genes

a unit of heredity consisting of a segment of DNA, a discrete particle that influences the characteristics of an individual

Alleles

one of the alternative forms of a gene; two alleles form a gene

-Dominant allele- is stronger and always shows up if present

-Recessive allele- is weaker and only shows up if both copies are recessive.

Locus

the specific position of a gene on a chromosome

Homozygous

describes an individual or gene that carries two identical alleles at a specific locus

-Ex: BB(homozygous dominant) or bb (homozygous recessive)

Heterozygous

describes an individual or gene that carries two different alleles at a specific locus

-Ex: Bb (one dominant, one recessive)

Standard notations for labeling generations (F0, F1, etc.)

-F0 = The first generation when tracking generations

-F1 = Offspring of original generation

-F2 = The next generation

-et cetera

Genotype

the genetic composition of organisms; also use as the term to describe the combination of alleles; is the genetic makeup, ex, Bb for eye color

Phenotype

the observable characteristics of an organism that are influenced by genes; it is the physical trait you can see, ex, brown eyes

What is a multi-locus (a.k.a. polygenic) trait?

Many genes contribute to a trait; a trait controlled by multiple genes instead of just one

-The environment interacts with genes for multi-locus traits, multi-locus traits are continuously distributed traits

What is a pleiotropic trait?

Happens when one gene affects multiple traits in the body.

How is variation maintained?

-Mendelian genetics- genes don’t blend; they are inherited as separate units(alleles)

-Recombination- during sexual reproduction, genes are mixed in new ways

-Multiple loci contribute to traits- some traits(like height or skin color) are influenced by many genes, not just one.

-Mendelian genetics is a partial explanation - Variation “hidden” in the form of recessive alleles (Blending inheritance is not true)

-Recombination is a partial explanation

-Mutations

-Understand the implications of multiple loci contributing to a trait

Where do novel traits come from, and how do species move beyond the apparent range of variation in the population?

-Mutations- random mutations create new traits that didn’t exist before

-Recombination- even without mutations, new combinations of genes can create unexpected traits

-Multiple genes- since many genes control traits, small changes over time can push species beyond their original range.

-Mendelian genetics is a partial explanation - Variation “hidden” in the form of recessive alleles (Blending inheritance is not true)

-Recombination is a partial explanation

-Mutations

-Understand the implications of multiple loci contributing to a trait

Recombination

is when genes get shuffled during reproduction, so each baby gets a unique mix of traits from their parents

-Homologous, replicated chromosomes tangle and break during meiosis

-Bits of one chromosome can be swapped between members of a homologous pair, = Can produce novel combinations of alleles in the genotype and novel combinations of traits in the phenotype of offspring crossing over

Mutations

errors in DNA replication; most mutations are harmful or neutral to fitness, but occasionally, a mutation can lead to a beneficial change and adaptation

What was Darwin’s definition of evolution?

Darwin described evolution as “descent with modification”

What is the modern definition of evolution?

From a modern genetic perspective, we define evolution as a change in allele frequencies from one generation to the next.

Know and understand the forces that change gene frequencies:

-Natural selection

-Mutation

-Gene flow (migration)

-Genetic drift (sometimes followed by the Founder’s Effect)

Natural selection

the process where organisms with traits that help them survive and reproduce pass those traits to their offspring.

mutation

is a random change in DNA that creates genetic variation in a population.

Gene flow (migration)

is the movement of genes from one population to another due to migration.

Migration → Mixing of genes → More genetic diversity.

Genetic drift (sometimes followed by the Founder’s Effect)

a random change in gene frequency in a population, usually affecting small populations the most.

-Genetic drift = Random changes in genes over time.

-Founder’s effect = Small group starts a new population, leading to reduced genetic diversity.

What is the difference between directional selection and stabilizing selection?

The difference between the two is that stabilizing selection favors the average traits and the extreme traits are reduced, while directional selection favors a trait changing, so the population starts changing toward that extreme.

-Ex: directional selection, imagine that giraffes with longer necks can reach more food, so over time, giraffes with longer necks become more common.

-Ex: stabilizing selection human birth weight- babies that are too small or too big may have health problems, so most babies are born with an average weight, keeping that trait stable over time.

How do random processes generate complex adaptations?

-Cumulative retention of small changes

-Each change increases fitness, giving individuals within populations small advantages over their competitors

Biological species concept

emphasizes reproductive isolation as the cause of speciation

-Gene flow

-Reproductive isolation

-Limitations of biological species concept

Gene flow

the exchange of genes(alleles) between individuals or populations of the same species; movement of genes(alleles) within groups and between groups

Reproductive isolation

there is no exchange of alleles between two groups of organisms

Limitations of biological species concept

biological species concept defines a species as a group of organisms that can mate and produce fertile offspring, however one of these limitations could be that the species is asexual.

Ecological species concept-emphasizes the role of natural selection.

-Natural selection maintains species boundaries even with limited interbreeding

-Two reasons hybrid populations may not grow

-Reinforcement- the fitness of hybrids produced by two species is lower than the fitness of the two cross-breeding species

-Character displacement- natural selection exaggerates differences between competing species or populations when they coexist

Types of speciation-Allopatric

happens when a population is split by a physical barrier( like a mountain, river, or ocean), causing them to evolve into different species over time.

Types of speciation-Sympatric

happens when a new species evolves without a physical separation.

Types of speciation-Parapatric

happens when a population is partially separated by different environments, but there’s still some contact between groups.

Homologies (Homologous traits)

Similarities based on a common ancestor. These are traits that different species have in common because they all inherited the trait from a common ancestor

Analogies (Analogous traits)

Similarities between species based on common function, with no assumed common evolutionary descent.

Convergent Evolution

Separate evolutionary development of similar characteristics in different groups of organisms. Convergent evolution leads to: Analogies (or Analogous traits)

Parallel Evolution

type of evolutionary process whereby species come to share phenotypic characteristics due to common ancestry. Parallel Evolution leads to: Homologies (or homologous traits)

Ancestral traits

Traits inherited by a group of organisms from their shared, common ancestor; also called “primitive” traits

Derived traits (and, shared derived traits)

Characters (traits) that evolved but are not seen in the ancestor

Adaptive radiation

The diversification of an ancestral group of organisms or a single species into new forms that are adapted to specific environmental niches. When a species, or group of species, has diverged into many variations of differing forms/species

What are characteristics that define primates?

-All primates have forward-facing eyes

-Primates tend to have large brains

-Hands and feet are prehensile, which means the hands and feet can grasp and hold things

-Tend to have slow life histories, they take their time growing, reaching maturity, and reproducing

-Most primates live in groups

-Have generalized diets that include multiple foods, omnivores

-Tend to have at least three forms of teeth: incisors, canines, and molars

-Most primates live in tropical rainforest areas close to the equator

Basic classification and characteristics of primate groups-Strepsirhini

snout, rhinarium(the moist, fleshy pad at the end of the nose), more acute sense of smell, also known as prosimians

-Many are nocturnal

-Many are solitary

-Some retain claws

-Some have acute sense of smell

-Wet, long noses

-Small eyes

-Tooth combs

-More developed sense of smell

Basic classification and characteristics of primate groups-Haplorhini

flatter noses without rhinarium( the moist, fleshy pad at the end of the nose seen in most mammals) , less reliance on sense of smell

-Dry noses

-Larger brains

-More complex social structures

-Diurnal, active during the day

-Highly social

Strepsirrhini (Prosimians)

Lemurs and Lorises

Haplorrhini

-Tarsiers

-Platarrhini = New World monkeys

-Catarrhini

-Old World monkeys

-Apes

-Lesser apes: Gibbons (some species are known as siamangs, but they are very similar)

-Orangutans

-Gorillas

-Chimpanzees/bonobos