Evolution Unit Class Notes

questions formatted from notes

Organisms evolve. True or False?

Organisms evolve. True or False?

False

Evolution happens to ———-

Populations

Descent with modifications

shared ancestry resulting in shared characteristics through an accumulation of differences

How does bacteria reproduce? significance?

binary fission- super short. Humans take ~23 years and have less offspring. Rate of reproduction for bacteria= much faster.

What does Charles Darwin observe

that lots of species on each island were very similar and with influence of other works, he notices descent with modifications.

species

have a way to create viable offspring

Mantises illustrate these 3 key observations of life.

1. Organisms are adapted for life in their biotic and abiotic environments

2. They many shared characteristics of life

3. The diversity of life

Evolution

the process by which species accumulate differences from their ancestors as they adapt to different environments over time.

Large population means that the rate of evolution is….

slower

Smaller population means that the rate of evolution is…

faster

Who developed a nested classification system? What is it called? What does it do?

Carolus Linnaeus.

binomial nomenclature

Groups similar species into increasingly inclusive categories.

Fossils are found in sedimentary rock in layers called…

strata

James Hutton’s idea

Earth’s features were formed gradually.

Charles Lyell’s idea

same geologic processes occur today as in the past at the same rate

Lemark’s Hypothesis of Evolution

2 principles to explain evolutionary change:

-use and disuse: extensively used parts get stronger and stay while unused parts start deteriorating in the population

-inheritance of acquired characteristics: modifications acquired in one’s lifetime can be passed to their offspring

Adaptations

inherited characters that enhance survival and reproduction in the environment

Natural Selection

Process where individuals with certain inherited traits tend to survive and reproduce at higher rates due to traits.

Darwin’s Observations:

most characteristics in the population must be inherited,

more offspring must be produced than can survive

the fittest offspring must be more likely to survive and reproduce.

What could Darwin infer?

Natural Selection, Adaptation, evolution

Factors that helped Darwin piece together Evolution?

Fossils, Biogeography, Homology, Direct Observation, etc.

How do bacteria transmit resistance to other bacteria?

Conjugation highway (through plasmid exchange)

What are morphological gaps between related groups explained by?

Branching and extinction events

Artificial selection

humans modify species by only breeding those with desired traits

True or false: populations don’t increase faster than critical resources?

False

Comparative Embryology

reveals anatomical homologies that are not visible in adult organisms but rather fetal.

Homology

similar anatomical structures used for different things due to common ancestry

Vestigial Structures

structures that are still present due to the functionality in ancestors

Molecular homologies

genetic code shared by all life- every organism has mitochondria so we can look at Cytochrome B to see gene similarity

Convergent Evolution

2 unrelated species evolve to have similar features through independent adaptations

Divergent Evolution

individuals in one species, or closely related species, acquire enough variations in their traits that it leads to two distinct new species

microevolution

change in allele frequencies in a population over a generation

3 mechanisms that can cause allele frequency change:

1. natural selection

2. genetic drift

3. gene flow

Mendel

genetic variation- differences in genes/ other DNA sequences among individuals with pea plants

At the gene level, genetic variation is quantified by the…

% of heterozygous loci in a population

At the molecular level, genetic variation is found by…

looking at the nucleotide sequences

Nucleotide variability rarely results in phenotypic variation because…

• most nucleotide differences occur in noncoding DNA segments (introns)

• variations in coding regions (exons) rarely change the amino acid sequence of the encoded protein.

What can phenotypic variation result from?

Environmental influences and genetic differences. But only the genetic part can have evolutionary consequences.

Sources of genetic variation:

mutations, gene duplication, or other processes, or sexual reproduction produces genetic variation by recombining existing alleles.

New alleles arise through:

mutations, change in nucleotide sequences of DNA.

Mutations can be caused by:

replication errors, exposure to certain types of radiation/ chemicals

Point mutations: frameshift, nonsense, missense, silent

a single nucleotide change can lead to different outcomes.

1. Frameshift: Caused by insertions or deletions, altering the reading frame.

2. Nonsense: Introduces a premature stop codon, truncating the protein.

3. Missense: Changes one amino acid in the protein, potentially affecting function.

4. Silent: Alters a nucleotide but does not change the amino acid sequence.

What mutations are harmful?

Those that delete, disrupt, or rearrange loci

Hardy Weinburg equilibrium conditions

1. No mutations

2. Random mating

3. No natural selection

4. Extremely large population size (no genetic drift)

5. No gene flow (immigration or emigration)

What mechanism consistently causes adaptive evolution

Natural Selection

Evolution by natural selection involves both “….” and “…”

chance and sorting; new genetic variations arise by chance and beneficial alleles are sorted and favored by nature

relative fitness

not direct competition but reproductive success. The contribution an individual makes to the gene pool.

Directional Selection

Favors individuals at one end of the phenotypic range

Disruptive Selection

Favors individuals at both ends of the phenotypic range

Stabilizing selection

Favors intermediate variants and acts against extreme phenotypes

What do the different types of selection do?

They are 3 ways that natural selection can alter frequency distribution

Sexual dimorphism

A difference in secondary sexual characteristics between species

Heterozygote Advantage

Occurs when heterozygotes have higher fitness than both kinds of homozygotes. ex: Heterozygotes have resistance to malaria

Pre-zygotic barriers

mechanisms that prevent mating or fertilization between different species. These barriers contribute to reproductive isolation and help maintain species integrity.

post-zygotic barriers

These are reproductive barriers that occur after fertilization ex: hybrid sterility, where hybrids are unable to reproduce, and hybrid inviability, where embryos do not develop properly. hybrid breakdown: 1st gen is viable but sterile

pre zygotic barriers- 4 examples

Geographic isolation, temporal isolation (time/period of reproductive cycle), behavioral isolation (right song/dance), mechanical isolation