Chapter 22: Descent with Modification: A Darwinian View of Life

22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species

• Evolution: Descent with modification, how species become different from their ancestor over time

• To prove evolution, Darwin studied the work of many other scientists through

  • Fossils: The remains or traces of organisms from the past

  • Strata: Superimposed layers of rock, the younger it is the higher, the older the deeper

  • Paleontology: The study of fossils, developed by Georges Cuvier

1. He thought that if geologic changes came from slow, continuous actions, Earth would be much older than most people thought

2. Cuvier’s hypothesis was specific, since it provided a way to test it (finding if the deeper rock is older than the newer rock through different dating methods), and so was Lamarack’s, though a lot of it was based in speculation

22.2: Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life

• Adaptations: Characteristics of animals that provide advantages for their survival in specific environments

• Natural Selection: Darwin’s theory for why adaptations occur, where animals with more advantageous traits survive and reproduce more, passing those traits to their offspring

• Artificial Selection: Humans modifying other species by selecting desired traits

• Darwin used two observations, where he drew two inferences:

  • Observation 1, Members of a population vary in these inherited traits

    • Inference 1, Individuals whose inherited traits give them an advantage leave more offspring

  • Observation 2, All species can produce more offspring than their environment can support, so many of these offspring can’t survive to reproduce

    • Inference 2, This leads to the accumulation of favorable traits over generations

1. Different species may undergo speciation, leading to higher diversity of life. At the same time, it also explains the unity of life because it shows how over time, the traits will stabilize and the population will mostly consist of organisms with the same trait.

2. Asian mountains, since many of the advantageous traits for them would be similar to the ones of the animals in the asian mountains, as they are similar environments with similar threats

3. The p allele would become more and more common, since plants with the allele would be more likely to survive to reproduce and produce more offspring.

22.3: Evolution is supported by an overwhelming amount of scientific evidence

• Many types of evidence for evolution

  • Direct observations, including the soapberry bug, whose beak evolved to the best length to feed on seeds, and antibiotic resistant bacteria, where the unaffected bacteria eventually evolved to become the majority

  • Homology: Similarity resulting from common ancestry

    • Homologous Structures: Show variations on a structural theme present in their common ancestor

    • Vestigial Structures: Features that served a function in the ancestor that is no longer useful

• Evolutionary Tree: Diagram to show evolutionary relationships among groups of organisms

• Convergent Evolution: Independent evolution of similar features

  • Analogous: When species share features because of convergent evolution

• Fossil record is also evolutionary evidence, can use DNA from them or shape of bones to compare to modern day organisms

• Biogeography: Scientific study of geographic distributions of species, influenced by many factors

  • Pangaea: The theoretical supercontinent from 250 million years ago

1. The mutation already occurred in which certain bacteria was drug resistant, but antibiotics killed the ones that weren’t, so natural selection occurred

2. a, the animals evolved from the same ancestor, so they share similar traits and bone structure. b, the advantageous mutation occurred in both populations, and natural selection occurred separately but resulted in similar traits

3. Broad, since this was around the period of Pangaea, where animals could roam freely among the different (modern day) continents

Chapter 23: The Evolution of Populations

• Microevolution: Evolution on the smallest scale, a change in allele frequencies over generations

  • Three main types. Natural selection, genetic drift, and gene flow (transfer of alleles between populations)

23.1: Genetic Variation makes evolution possible

• Genetic Variation: Phenotype variations, differences among individuals in composition of genes/DNA sequences

  • Without genetic variation, evolution can’t occur

• Neutral Variation: Differences in DNA that don’t provide a genetic advantage/disadvantage

• Mutation rates are low for plants and animals (1/100,000), and even lower in prokaryotes, but since prokaryotes reproduce more faster there is lots of genetic variation

  • In sexually reproducing organism, the genetic variation usually comes from the combo of parents’ alleles

    • 3 factors, crossing over, independent assortment of chromosomes, and fertilization

1. Natural selection “selects” favorable alleles from the already existing gene pool. Without variation, there is nothing that provides an advantage or disadvantage, so there is nothing to choose, and no evolution can occur

2. They have advantages to survival and reproduction.

3. Asexual reproduction leaves less chance for genetic variation, so genetic variation happens much more slowly

23.2: The Hardy Weinberg Equation can be used to test whether a population is evolving

• Population: Group of individuals of same species that live in same area and interbreed

• Gene Pool: Population’s genetic makeup, consists of copies of every type of allele of every member of the population

• Hardy Weinberg Equilibrium: Population is not evolving so allele and genotype frequencies stay constant from generation to generation

• p: Frequency for allele of dominant trait

  • p²: Genotype frequency of dominant homozygote

• q: Frequency for allele of recessive trait

  • q²: Genotype frequency of recessive homozygote

• 2pq: Genotype frequency of heterozygote

• p + q = 1

• p² + 2pq + q² = 1

1. p² = 85/700 = 0.12, 2pq = 320/700 = 0.46, q² = 295/700 = 0.42. So, p = 0.35, q = 0.65.

2. q = 0.45. So, p² = 0.2, q² = 0.3, and 2pq = 0.5

3. The population most likely is evolving, since there is a factor influencing natural selection.

23.3: Natural selection, genetic drift, and gene flow can alter allele frequencies in a population

• Adaptive Evolution: Caused by natural selection, traits that enhance survival/reproductive frequency tend to increase over time

• Genetic Drift: Chance events that cause allele frequencies to shift unpredictably

  • Founder Effect: Small part of population becomes isolated from rest of it and establishes a new population with different gene pool

  • Bottleneck Effect: Severe drop in population size, so gene pool is altered

  1. More significant in small populations

  2. Can cause allele frequencies to change at random

  3. Can lead to loss of genetic variation within populations

  4. Can cause harmful alleles to become fixed (100% frequency)

• Gene Flow: Transfer of alleles into or out of population due to movement of fertile individuals

1. Genetic drift is due to random chance, and there is no way to predict which alleles will be favored. Natural selection only favors advantageous traits, so the traits that will be favored are predictable.

2. a, Gene flow is more gradual and relies on natural selection, genetic drift is sudden. b, gene flow introduces a gene into the population which then relies on natural selection, genetic drift is often random

3. The hardy weinberg equilibrium will most likely occur

23.4: Natural selection is the only mechanism that consistently causes adaptive evolution

• Relative Fitness: The contribution an individual makes to the gene pool of the next generation relative to the others

• Directional Selection: Conditions favor one extreme, shifting the curve in one direction.

  • Common when population’s environment changes or members of population migrate habitats

• Disruptive Selection: Conditions favor both extremes

  • ex. Birds with small bills can feed on soft seeds, large bills are good at cracking hard seeds, intermediate are inefficient at both

• Stabilizing Selection: Conditions favor intermediate variants, reduces variation

  • ex. Babies too light or heavy have higher rates of mortality

• Sexual Selection: Charles Darwin found process in which individuals with certain traits are more likely to gain mates

  • Sexual Dimorphism: Difference in secondary sexual characteristics between males and females of species because of sexual selection

• Intrasexual selection: Individuals of one sex (usually females) select mates from the other sex, who compete for mates

  • Sometimes these traits make them more susceptible to threats, but benefits outweigh the risk

• Balancing Selection: Preserves variation, maintaining 2+ phenotypic forms in a population

  • Frequency Dependent Selection: Fitness of phenotype depends on how common it is in the population

    • ex. Some fish are left mouthed and right mouthed, prey guard against whatever is more common so the less common one is favored, which differs from year to year

  • Heterozygote Advantage: Natural selection maintains two or more alleles at the locus, defined by genotype not phenotype

• Why can’t natural selection make perfect organisms?

  • Selection can only act on existing variations

  • Evolution is limited operating on existing traits

  • Adaptations are often compromises

  • Chance, the environment, and natural selection interact

1. Bad, since relative to the others in its population it can’t reproduce so it has terrible relative fitness

2. It manipulates the gene pool of the population to favor certain traits and force adaptation

3. Stabilizing, since it has a heterozygote advantage

Chapter 24: The Origin of Species

• Speciation: The process where one species splits into two

  • Forms a bridge between micro and macroevolution

    • Macroevolution: The broad pattern of evolution above species level

      • ex. origin of new groups of organisms through speciation

24.1: The biological species concept emphasizes reproductive isolation

• Biological Species Concept: Defines species as a group of populations whose members can interbreed, but can’t do so with other groups of animals

• Reproductive Isolation: Existence of biological barriers that prevent members of two species from producing fertile offspring

  • Limits formation of hybrids

  • Prezygotic Barriers: Block fertilization, through one of three ways—Keeping them from attempting to mate, preventing attempted mating from working, or hindering fertilization

  • Postzygotic Barriers: Contribute to reproductive isolation after hybrid zygote formation

• Morphological Species Concept: Distinguishes species by body shape and other structural features

• Ecological Species Concept: Defines species terms of its ecological niche, how members of the species interact with nonliving and living parts of environment

1. a all of them except biological. b biological

2. habitat isolation

24.2: Speciation can take place with or without geographic separation

• Allopatric Speciation: Gene flow interrupted when population is divided into geographically isolated subpopulations

  • Occurs because of geographic isolation

• Sympatric Speciation: New species from the same ancestral species living in same area

  • Occurs because of reproductive isolation

• Polyploidy: Species originates from accident during cell division which causes extra sets of chromosomes

  • More common in plants than animals

• Autopolyploid: Individuals with 2+ chromosomes all derived from a single species, causes reproductive isolation

• Allopolyploid: Fertile when mating with each other but can’t mate with parent species, many things can change things from sterile hybrid into one

• Sexual selection can cause sympatric speciation, and so can habitat diffrentiation (exploits habitat or resource not used by parent population, causes habitat isolation)

1. Allopatric, specifically in animals. Allopatric involved changing geographic locations, sympatric is within the same habitat

2. Sexual selection and habitat differentiation

3. Isolated island of the same size, since they are less likely to return to the old population and more likely to start a new species via the founder effect

4. Idk

24.3: Hybrid zones reveal factors that cause reproductive isolation

• Hybrid Zone: Region where closely related members of different species meet and mate

  • Usually located where habitats of interbreeding species meet, isolated patches scattered across the landscape. Usually stable

  • Can be a source of genetic variation to improve the ability of one or both of the parent species to cope with changing environment

• Reinforcement: Hybrid has a lower fitness than its parents

• Some hybrid zones have reinforcement weaken over time, so the species’ gene pools fuse

1. Hybrid zones are areas where similar species meet and mate, creating hyrids. These hybrids, if they survive and pass on their genes, may begin to form new species.

2. a. hybrids would die out and the two species would remain seperate. b. hybrids would continue to breed and possibly eventually form a new species

24.4: Speciation can occur rapidly or slowly and can result from changes in few or many genes

• New species can form rapidly once divergence starts, but it can take millions of years for it to happen

  • Time interval between speciation varies, from a few thousand years to tens of millions of years

  • Particular genes are involved in some cases of speciation, but it can be driven by a few or many genes

1. Speciation can take millions of years to happen

2. Idk

3. Meiosis maybe?

Chapter 25: The History of Life on Earth

25.1: Conditions on Early Earth made the origin of life possible

• Four main stages that may have led first living cells to appear

1. Abiotic synthesis of small molecules (amino acids & nitrogenous bases)

2. Joining of these molecules into macromolecules (proteins and nucleic acids)

3. Packaging them into protocells

   1. Protocells: Droplets with membranes that maintained an internal chemistry different from that of their surroundings

4. Origin of self replicating molecules

• In 1920s Haldane thought Earth’s early atmosphere was a reducing environment, with the electrons coming from lighting and UV radiation

  • Early oceans were “primitive soup”, a solution of organic molecules

• Miller Urey in 1953, early earth conditions yielded amino acids

• Another hypothesis, organic compounds produced in deep sea hydrothermal vents

  • Hydrothermal Vents: Areas on the seafloor where heated water and minerals gush from Earth’s interior into ocean

    • Relase very hot water

  • Alkaline Vents: Other deep sea vents, releasing warm water with a high pH that may have been more suitable for life

• Self replicating molecules and a metabolic source of building blocks found in vesicles, which can occur spontaneously when lipids or other organic moleules are added to water

• First genetic material was probably RNA, which plays a central role in both protein synthesis and acts as an enzyme like catalyst

  • Ribozymes: RNA catalyzes that are similar to enzymes. Some make complementary copies of short pieces of RNA

• In Early Earth, a versicle that had self replicating catalytic RNA which could grow, split, and pass its RNA to daughters, the daughters would b protocells

1. Amino acids arose naturally during early earth

2. First cells, which are the basis of all living things

3. Not sure

25.2: The fossil record documents the history of life

• Different types of fossils

  • Sedimentary rock, where most fossils are found

  • Mineralized organic matter, since some minerals seep into and replace organic matter

  • Trace fossils, such as footprints, burrows, or traces of activity

  • Amber, which preserves organisms in hardened resin

  • Frozen soil, ice, and acid bogs can preserve the body of larger organisms

• Radiometric Dating: Based on decay of radioactive isotopes

  • Half Life: Rate of decay, time required for 50% of the parent isotope to decay

1. Tells us how much we evolved from our ancestors

2. 4 half lives?

25.3: Key events in life’s history include the origins of unicellular and multicellular organisms and the colonization of land

• Three eons in the geologic record, the Hadean, the Archaean, and the Proterozoic, lasting about 4 billion years in total

• First single celled organisms (prokaryotes) are from 3.5 billion years ago, coming from fossilized stromatolites

  • Stromatolites: Layered rocks that form when certain prokaryotes bind thin films of sediment together

• “Oxygen revolution”, O₂ level shot up quickly between 1% and 10% of today’s present level

• Endosymbiosis led to first single celled eukaryotes

  • Serial Endosymbiosis Hypothesis: Mitochondria evolved before plastids through endosymbiotic events

    • Inner membranes have enzymes and transport systems like those of plasma membranes of bacteria

    • Cellular machinery, such as ribosomes

    • Ribosomes of mitochondria and plastids more similar to bacterial ribosomes than cytoplasmic ribosomes of eukaryotic cells

• About 541 million years ago multicellular eukaryotes appeared

• Cambrian Explosion: Present day animal phyla suddenly appeared (535-525 million years ago)

• Larger forms of life (fungi, plants, animals) began to colonize land about 500 million years ago

1. Many developed as anabolic organisms

2. Mitochondria are present in all eukaryotic cells

3. ?

25:4: The rise and fall of groups of organisms reflect differences in speciation and extinction rates

• Plate Tectonics: Continents are part of great plates of Earth’s crust that float on the mantle

  • Continental Drift: Movements in the mantle that cause plates to move over time

• Pangaea: The supercontinent that all continents used to be a part of

• Mass Extinction: Disruptive change to global environment causes rate of extinction to increase dramatically

  • Permian 252 million years ago, claimed 96% marine animal species, during most extreme episode of volcanism in the pas 500 million years

    • Caused CO₂ levels to increase enough to warm the Earth by 6°C

    • Ocean acidification, so less calcium carbonate, needed by reef building corals and shell building species

  • Cretaceous 66 million years ago, killed more than half all marine species, killed dinosaurs and many species of plants and animals

    • Asteroid blocked sunlight, caused sudden drop in global temps

• Adaptive Radiations: Groups of organisms form new species whose adaptations let them fill different niches in their communities

1. Changes in climate, natural disasters

2. New ecological opportunity

3. A bunch of animals and people would die, might mark the end of certain species and take millions of years to recover

25.5: Major changes in body form can result from changes in the sequences and regulation of the developmental genes

• Heterochrony: Evolutionary change in rate or timing of development

• Pedomorphosis: When sexually mature too early compared to other organs, may retain baby features

• Homeotic Genes: Determine basic features such as where wings will develop on a bird

  • Hox Genes: Products of one class of homeotic genes, provide positional info in embryo

    • As more and more are duplicated more are able to turn on and off and form new structures

1. Idk

2. Turns on or off at places it needs to replicate

25.6: Evolution is not goal oriented

• Evolutionary trends don’t imply a drive towards a specific phenotype

• Trends can come from natural selection or species selection

1. It is used to benefit organisms and help them best survive, the eye is advantageous so it is passed on by the organisms with it, who have higher relative fitness

2. As they begin to get exposed to the virus, the ones who are resistant will survive and reproduce