Theories of Evolution

Question 1

What is a theory?

Answer 1

An explanation for how something that takes into account known scientific evidence and can be modified according to newly found evidence and data.

Question 2

What is a law?

Answer 2

A law is a description of patterns of what always happens and usually occurs in physics.

Question 3

Before the 18th century?

Answer 3

• before the 18th century people strongly believed that organisms were made one way at creation and remained the same until now

Question 4

During the 18th century?

Answer 4

• Buffon: said he thought species could change and those changes could lead to new species
• Linnaeus: thought there were a few species of creation who became hybrids which formed in species later (invented binomial nomenclature)
• Erasmus Darwin: (Charles’ grandfather) believed that all life came from a single source

Question 5

Lamarck’s Theory: Evolution through the inheritance of acquired traits

Answer 5

• first theory that involved a mechanism (a system of how something happens), the mechanism was the inheritance of acquired traits
• believed in spontaneous generation
• thought an organisms force of desire will create a trait to fulfill that desire within their lifetime and the use or disuse of that trait determined weather or not it would be passed on to its offspring
• example: giraffes got a long neck because they had a desire to reach the food higher up on trees so they grew their necks in their lifetime and the use of the long neck determined that it would be passed on

Question 6

Darwin’s Theory of Evolution through natural selection on the HMS beagle

Answer 6

• took a trip around the world on HMS beagle and observed the following
• unusual fossils resembling giant sloths and armadillos that lived in the same region
• from this he determined that life forms descended from fossils
• species in South American tropics didn’t represent those in African tropics
• from this it was concluded that species evolve independently if isolated

Question 7

Darwin’s Theory of Evolution through the process of Natural Selection: the Galapagos Islands

Answer 7

• the Galapagos islands has 13 species of similar finches that are found nowhere else but resembled a species living off the coast of South America
• evolution from a single species in South America that arrived to Galapagos and evolved to be different from the original species because of a different habitat
• he found fossil deposits of coral at an elevation of 3000m in the Andes
• severe earthquake lifted portions of the East coast 3m upwards
• geological forces responsible for location of fossils and mountains

Question 8

After Darwin’s voyage

Answer 8

• continued to gather evidence, perform investigations, and convene with other biologists
• interest in artificial selection, recognized that all species possessed inherited variations that could be selected for
• reasoned that if people could artificially select for traits than the environment could have the same affect on species
• malthus: a math paper that said that all species produced more offspring than could survive
• Darwin recognized that if so many offspring were being born they would have to compete against each other for survival
• Wallace: a naturalist working in Malaysia who came up with the same findings independently then sent a letter to Darwin
• colleagues convinced Darwin to publish a paper on his findings with Wallace’s paper

Question 9

Theory of evolution through Natural Selection

Answer 9

1) observation: individuals within a species exhibit many inherited variations
1) inference: individuals of the same species are in a constant state of struggle for survival
2) observation: every generation produces more offspring than can survive to reproduce
2) inference: individuals with more favorable variations are more likely to live on to reproduce to pass on its advantageous variations. Survival is not random it is determined through natural selection
3) populations of a species tend to remain stable in size
3) since individuals with more favorable variations contribute proportionally to succeeding generations their favorable traits become more common and this is evolution

Question 10

Key points to Darwin’s theory of Natural Selection

Answer 10

5 distinct areas
1) overproduction: more offspring produced than can survive, reproduce and live to maturity
2) competition: organisms must compete for food, habitat, water, and shelter
3) variation: differences in species that are passed on to their offspring
4) survival of the fittest (natural selection): individuals that are well adapted to their environment are more able to compete, survive, and reproduce
5) origin of new species by inheritance of successful variations: over generations, new species arise through inherited genes; a new species is produced

Question 11

Peppered moth case study

Answer 11

Light colored moth called (typica) were prominent before the industrial revolution when their white speckled wings blended in with the white birch trees. Post industrial revolution the trees turned black because of pollution which led to a new type of moth (carbonaria). They had dark wings that were selected for because they blended in with the dark trees so they became prominent as the white ones died out. Bernard Kettlewell conducted a capture and release experiment where there were different moths in the black woods of Birmingham and the white woods of Dorset. When he captured he marked the bottoms of their wings with cellulose paint and the survival was proportionate to camouflage efficiency. His experiment was under criticism but his findings were generally accepted.

Question 12

Giraffes and Natural Selection

Answer 12

Originally it was mostly short necked giraffes existed but some variation still existed. As fruit on the shorter trees dwindled the giraffes with a variation with longer necks could reach the trees up high and they were more likely to survive.

Question 13

Survival of the fittest

Answer 13

fitness is referring to a level of reproductive success.
- example: only giraffes with a adapted longer neck could survive and reproduce, over time the population of giraffes changed because that adaptation was passed on

Question 14

Sources of inherited variation

Answer 14

• even though Darwin new variation existed he didn’t know where it came from
• it wasn’t until the 1930s that enough information was gathered to understand genes hereditary
• variation comes from mutations and sexual reproduction

Question 15

Mutations

Answer 15

• mutations are changes in a DNA segments genes
• DNA: deoxyribonucleic acid and is a heriditary material that is passed on
• genes: segments of DNA
• DNA is in chromosomes of cells
• composed of four nucleotide bases, ATGC
• nucleotide bases together for a protein and are called codons
• genes code for certain inherited traits
• mutations are random changes in DNA sequence
• insertion, deletion, substitution, and chromosomal re arrangements (duplication, inversion, and deletion)
• these changes may or may not affect the function or expression of a gene
• they provide a continuous supply of information

Question 16

Causes of mutation

Answer 16

• experimental factors
• errors in DNA production and replication
• relatively rare in individuals because there is only one set of gametes, ones mutation per sex cell
• mutagens have a higher rate of mutation

Question 17

Super hybrids

Answer 17

• Mutation in the Myostatin MSTN gene causes continuous growth and strengthening

Question 18

Types of mutation

Answer 18

1) neutral mutations (most common)
2) harmful mutations (more common than beneficial ones)
4) beneficial mutations
- the environment determines which mutation is selected for, beneficial mutations are selected for and lead to adaptations

Question 19

Adaptations

Answer 19

• accumulation of traits which improve a species ability to survive
• its mechanism is natural selection
  1) structural: modification of structures that allowed special functions
• example: fingers, bat wings, leaves of pitcher plants
  2) physiological: the change in the chemicals an organism produces
• example: venom, digestive enzymes in the leaves of a pitcher plant
  3) behavioral: actions and instincts of an organism
• example: hibernation, migration

Question 20

Addressing misconceptions

Answer 20

• mutations don’t occur as needed, they are random with harmful being more common than beneficial
• since harmful mutations are more common they can cause extinction, this is false because beneficial mutations are selected for by the environment and favors an organisms fitness
• evolution isn’t pure chance, beneficial mutations are selected for and can accumulate, beneficial mutations give individuals improved survival and enhanced reproductive fitness

Question 21

Sexual Reproduction and Variability

Answer 21

1) asexual reproduction
- less chance for variability because there is only one parent
- reproduce through mitosis and binary fission
- only inherit genes from that parent
2) sexual reproduction
- inherit two sets of gametes so more chance for variability
- enhanced mutation
- production of offspring by the union of sex cells (gametes) from two different parents
- gametes: sex cells
- sematic cells: not sex cells

Question 22

Reasons why sexual reproduction has more variability

Answer 22

1) two copies of each gene one from each parent and they make different combos
2) assortment of genes an offspring inherits from either parent is random, the greater number of genes, the more combos, the greater variability
3) sexually reproducing species chose different mates, combos of parents means a different combo of genes

Question 23

Genetic mechanisms and Darwin’s theory

Answer 23

1) inherited characteristics: determined by genes, organisms possess thousands of genes
2) population variability: there’s variability within a population
3) source of new variation: new traits when genes are mutated
4) natural selection: genes determine traits that enhance an individuals chance of survival, and they will produce more offspring with the same advantageous gene
5) evolutionary change: over many generations, individuals carry genes that determine the most favorable traits for survival, these genes become more common in the population

Question 24

Courtship rituals

Answer 24

• used to determine the choosing of a mate
• is affected by traits that lead to adaptation which can result in reproductive isolation then speciation
• example: necking fights, plumage of birds in the galapagos
• the expenditure of energy to upkeep courtship rituals is indicator of the ability to get food and survive so those beneficial traits are passed on

Question 25

Evolution of a species

Answer 25

• species: a group of naturally producing and interbreeding organisms capable of producing fertile offspring
• population: a group of species living in the same region at the same time
• speciation: formation of a new species
• genes pools can be isolated resulting in adaptations to different environments
• there are two types of isolation
  1) geographic isolation
  2) reproductive isolation

Question 26

Geographic isolation resulting in allopatric speciation

Answer 26

1) physical barrier
2) makes two different environments
3) different environments bring about different mutations
4) natural selection works independently
5) inherited traits makes two groups too different to interbreed
- allopatric speciation: speciation with geographic isolation

Question 27

Reproductive Isolation

Answer 27

• inhability to produce fertile offspring
• can occur due to geographic, behavioral, or temporal changes
• differences in chromosomes and biochemical differences
• sympatric speciation: speciation in the same geographic area

Question 28

Bonobos and Chimpanzee’s

Answer 28

1) lived on the same side of the congo
2) river fell so some crossed to the other side
3) river rose and made a geographic barrier
4) natural selection works independently
5) allopatric speciation
6) couldn’t interbreed making two different species

Question 29

Hybrids

Answer 29

1) female horse + male donkey = mule
2) male zebra + females horse = zorse
3) male lion + female tiger = liger
4) male tiger + female lion = tigon

Question 30

Why are hybrids sterile

Answer 30

• the number of chromosomes, location of theme, and types of genes make their sex cells incompatible
• during meiosis chromosome sets are split in half then pair with another pair, since the hybrids chromosome set can’t split in half again it can’t pair up to produce more offspring
• formation of sterile hybrids maintains biodiversity
• hybrids are not likely to form in the wild because of geographic barriers and courtship rituals, it is energetically wasteful to produce a sterile hybrid
• prevents hybridization
• barriers of hybridization prevent the extinction of a species (ex. birds in Hawaii)

Question 31

Convergence and Divergence

Answer 31

1) stability: the more variation in a population the greater the chance the population will survive
2) convergence: different species may adapt similarly due to similar environments (example: marsupials and mammals)
3) divergence: similar species became different due to different environments: do not interbreed and each undergo natural selection (example. Darwin’s finches)

Question 32

Plant Speciation

Answer 32

• a single population split into distinct breeding populations in a single geographic region (sympatric speciation)
• sudden process
• mutation results in a double # of normal chromosomes (polyploids, called polyploidy)
• tend to be larger and better in plants
• healthy individuals
• reproductively isolated from the rest of population
• diploid: one set of gametes, two gamets
• haploid: one gamete
• polyploidy: doubling a chromosome set
• autotetraploidy: polyploidy to a chromosome set of a same species
• allotetraploid: polyploidy to a gamete from two different species
• meiosis: split of a gamete set

Question 33

Rate of Evolution

Answer 33

gradualism: speciation takes place over time at a slow and constant rate
punctuated equailibrium: proposed by Eldrige and Gould, many species evolve in evolutionary time, usually in isolated population where intermediate fossils are rare, after a burst of evolution there is no change

Question 34

Antibiotic resistance

Answer 34

• over prescriptions, not completing prescriptions, and incorrect use led to rapid evolution of antibiotic providing resistance (not immunity). Bacteria can pass on resistant genes through plasmids and phages
• they can adapt quickly due to a short generation time

Question 35

Macroevolution: Diversification and Extinction

Answer 35

• earth is at an increase of biodiversity
• biodiversity is stopped by extinction events
• example: the burgess shale

Question 36

Causes of mass extinction

Answer 36

• cataclysmic events
• tectonic movements
• asteroid impact (ended the Mesozoic era)
• evidence: Chicxulub crater
• human impact is expected to be the 6th mass extinction, first one not to be natural