First test Flashcards

Question

Scientist working at the same time as Darwin, independently came up with the conclusion that evolution occurs by natural selection.

Answer 1

Alfred Russel Wallace - worked in Indonesia

Answer 2

Evolutionary modification that improves the chances of survival and reproductive success.

Answer 3

1. A change in genetic frequency in a population of organisms through time. 2. The diversification of biological life from the advent of the earliest microbes to modern life forms. 3. A natural process that provides sufficient explanation for all natural phenomena without having to appeal to purpose or design.

Answer 4

1. Natural Selection 2. Genetic Drift 3. Emigration/immigration 4. Founder's effect 5. Sexual Selection

Answer 5

The genetic drift that results when a small number of individuals from a large population colonize a new area. (like birds flying to a new area), they bring only a fraction of the genetic variation present in the original population.

Answer 6

The production of random evolutionary changes in small breeding populations. one allele may be eliminated by chance. Decreases genetic variation within a population, increases genetic differences among different populations.

Answer 7

Migration of breeding individuals between populations causes a corresponding movement of alleles, or gene flow. Counteracts the effect of natural selection and genetic drift. Reduces the amount of variation between two populations

Answer 8

A special case of natural selection. An organism's ability to obtain a mate (at any cost!). Peacocks tails, fighting seals, dancing fruit flies. Features can be harmful to the individual's survival (peacock tails can also attract predators). Irish Elk antlers

Answer 9

Francis Crick - Discovered DNA - DNA too complex to have arisen from any reasonably known or postulated condition on earth. Suggested a seeding event (from outer space). Craig Venter - sequenced the human genome - Life occurs everywhere throughout the universe. Life on our planet most likely is the resultof a panspermic event (seeding from outer space). Need the right tools to prove life happens.

Answer 10

Lack of compelling de-randomizing mechanism. Life must be organized from intelligent design if we accept that there is a creator. If evolution from nonlife, doesn't it require a world changing at a speed conducive for evolution? (how could one event have sparked it and then everything slowed - inconsistent). Embracing a naturalistic explanation for life's origins advanced by philosophical materialists who often used the theory to support antitheistic philosophies.

Answer 11

1. Marxists 2. Eugenics movements and Nazism 3. Freud 4. Scientific Materialism (Naturalism) 5. Situational ethicists 6. Deweyan educational philosophy 7. Others

Answer 12

Before 1850s Christian explanations pervaded science and origin of life. Many believed in the immutability of species. Some Christians had ideas: Augustine (God is unchangeable, so he must create from nothing, not from himself), Linnaeus, conservative theologians BB Warfield, CHarles Hodge ("if God creates, it matters not how he creates")

Answer 13

Each individual species on the planet was specially created by God and could never fundamentally change. What supports it: 1. catastrophism - earth's geology created by big events like volcanos or floods (Noah's) - these caused extinction of some species. 2. orderly universe created by God 3. Ussher's Chronology- literal interpretation of the old testament - young earth 4000 BC

Answer 14

Before Darwin, in Paley's book, influenced him - Saw scientific theory as a way to think God's thoughts after him - was a perspective that attempted to understand God's purpose by examining natural features - many embraced catastrophism, but then uniformitarianism - generated a debate on age of earth

Answer 15

1. God's purposes for creation could be learned thru study of nature 2. Catastrophism was raised to dogma 3. Immutability of species

Answer 16

That they could prove the existence of God and describe him using nature alone, without the scriptures or miracles. The perfection of an organism adaptation to the environment was proof that God designed all life.

Answer 17

Lyell - the mountains, valleys, and other features were not created in their present forms, but were formed slowly over long periods of time, so the earth is old. "Principles of Geology" Darwin took a copy onthe Beagle

Answer 18

put fossils in evolutionary sequence. Believed that the long neck of the girffe developed when short-necked ancestors ate leaves instead of grass. Offspring inherited the neck and stretched it longer.(inner drive for self improvement)

Answer 19

The slow and gradual changes that happen within an organism or society to make a better environmental fit . An example of gradualism is the stripes of a tiger developing over time so they are better able to hide in tall grass.

Answer 20

combined theory of natural selection with concepts of modern genetics and inheritance (Neo-Darwinian Synthesis)

Answer 21

Father of genetics. 1860s but work was rediscovered in 20th century.

Answer 22

An allele that is the only variant that exists for that gene in all the population. A fixed allele is homozygous for all members of the population. The term allele normally refers to one variant gene out of several possible for a particular locus in the DNA

Answer 23

Allelic frequencies do not change in a population of random mating individuals - segregation and recombination do not alter genetic frequencies - allelic ratios (producing phenotypic ratios) do not equal genotypic ratios. - evolution must be acting on a population because allele frequencies in nature are often significantly different from what the HW principle would predict.

Answer 24

1. That low frequencies of heterozygotes produce rare homozygous recessive (hard to lose alleles that are lethal recessive). 2. Hereditary mechanisms by themselves do not alter genetic frequencies.

Answer 25

1. Infinite population size - it is a statistical tool, so needs a large population so that the effect of chance is small. Allele frequency in a small population are more likely to be affected by chance events 2. No migration - no exchange of genes with other populations that might have different allele frequencies (no migration in or out) 3. No net mutations - the relative numbers of B and b must not change due to mutations 4. Random mating - no selection of mates based on the genotype. equal probabilities of matings among genotypes 5. No natural selection - if it occurs, certain genotypes are favored over others. Consequently the allele frequencies will change and the population will evolve.

Answer 26

They are evolving. Two main causes: natural selection genetic drift other causes

Answer 27

1. variation within populations | 2. variation between populations

Answer 28

a. quantitative characters b. polymorphic traits c. ways to measure genetic diversity (%heterozygotes vs. # of different nucleotides in a base pair sequence, distribution of genes on different chromosomes)

Answer 29

1. Mutation | 2. Recombination of traits due to sexual reproduction

Answer 30

- point mutations (silent, each person has some, a change in one base pair) - gene or chromosomal duplication (chromosomes duplicate) - nondisjunctions (when one chromosome doesn't split it's pair properly, resulting in an unequal distribution of chromosomes - inversion -chromosome segment flips - translocation - chromosome segment reattaches to another chromosome (bison and cattle 2n=60, sterile) - chromosomal fusion 2n-46 (human), 2n-48 (chimp) because human chromosome #2 fused, so we have less than apes.

Answer 31

1. diploidy 2. heterozygotic advantage 3. frequency dependent selection 4. neutral variation

Answer 32

a state of being diploid, that is having two sets of the chromosomes (and therefore two copies of genes), especially in somatic cells

Answer 33

the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype (example: sickle cell anaemia)

Answer 34

evolutionary process by which the fitness of a phenotype depends on its frequency relative to other phenotypes in a given population. - In positive frequency-dependent selection, the fitness of a phenotype increases as it becomes more common. - In negative frequency-dependent selection, the fitness of a phenotype decreases as it becomes more common

Answer 35

differences in DNA sequence that do not confer a selective advantage or disadvantage; recessive alleles in diploid eukaryotes. balancing selection. occurs when natural selection maintains two or more forms in a population

Answer 36

1. Phenotype variation | 2. Maintains sexual reproduction in the face of disadvantages of sexual reproduction

Answer 37

bell curve shifts to one side - environmental changes favor the selection of more suitable phenotypes, causing the distribution to shift - peppered moths are an example

Answer 38

From a bell curve to a curve that looks like two humped camel - environmental changes favor the selection of more suitable phenotypes at both extremes of the normal distribution, causing a split. - example is the finches on the Galapagos is an example -limited food supply favored wide beaks that could strip off bark to get insects and long beaks to open cactus fruits (two extremes)

Answer 39

bell curve gets narrower - in a stable environment stresses tend to weed out unsuitable phenotypes, making the population more uniform

Answer 40

1. Directional selection 2. Diversifying Selection 3. Stabilizing selection

Answer 41

Advantages: More variation assists with survival. It increases the chance that at least some offspring of a parent survive. Example: if a deadly infection occurs in the population. Greater variety increases the chance that some of the population will survive. Disadvantages: Requires two parents. So a population of animals reproducing sexually would produce only half as many offspring as a population reproducing asexually, such as starfish do.

Answer 42

Related to sexual selection - an aggregation of male animals gathered to engage in competitive displays, lekking, to entice visiting females which are surveying prospective partners. Birds of paradise, turkeys, etc.

Answer 43

1. Production of new (RNA) molecules in lab to expedite the evolution of metabolite microbes. (CRISPR, used in gene therapy) 2. agricultural benefits associated with avoidance of pesticide resistance (roundup ready crops) 3. Understanding antibiotic resistance -

Answer 44

False. The occurrence of mutations is random. Natural selection can help retain and increase the proportions of individuals with beneficial mutations in a population (or reduce or eliminate those with harmful ones), but nothing but chance influences the initial mutation.

Answer 45

mutation, genetic drift, gene flow, natural selection (these are all examples of microevolution)

Answer 46

the migration of individuals between populations. Causes a corresponding movement of alleles that chan cause changes in allele frequencies

Answer 47

Phenotype - even though it is an expression of the genotype. NS acts on the heritable component of the phenotype, which represents an interaction of all alleles in the organisms genotype. It is rare that a single gene pair has complete control over a single phenotypic traits (like Mendel's peas). More common is the interaction of several genes for the expression of a single trait. Many plant and animal characteristics are under polygenic control

Answer 48

Traits such as human height are under this type of control, when a range of phenotypes occurs, with most of the population located in the middle (median) range and few at the extremes.

Answer 49

a measure of the ability of an organism (owing to its genotype) to compete successfully and make a genetic contribution to susequent generations. Organisms favored by natural selection exhibit high fitness.

Answer 50

No. it "weeds out" individuals with phenotypes less adapted to environmental challenges, while allowing better adapted individuals to survive and pass their alleles on to their offspring. NS is the only process known that brings genetic variation into harmony with the environment and leads to adaptation.

Answer 51

The presence in a population of two or more alleles for a given locus (example, blood types in humans A, B, or O, )

Answer 52

Peppered moths - increase in melanin in the varieties living in cities. So they are darker and blend in with the soot better on trees in the city. In areas in the country, the trees have lichen and are mottled, so the moths are "peppered" with light colors. This allows them to blend in better so they can rest during the day protected from predators. They are polymorphic.

Answer 53

Evolution that involves small, gradual changes within a population. Also defined as one that involves changes in allele frequencies over successive generations.

Answer 54

(s) is the mutant allele for sickle cell - produces an altered hemoglobin molecule that deforms the red blood cells (RBCs) and makes them look like a sickle (crescent moon). Then they clog capillaries and are destroyed in the liver, spleen or bone marrow. If an individual is homozygous (ss) for sickle cell, they usually die early. Heterozygous have both alleles (S and s). Ss are more resistant to a type of malaria than SS individuals (the s abnormal hemoglobin is the one that makes them resistant). SS and ss individuals are at a disadvantage because even though they don't have sickle cell, both of them are more susceptible to the type of malaria.

Answer 55

Ernst Mayr - groups of interbreeding natural populations which are reproductively isolated from other such groups. They have a common gene pool. Only applies to sexually reproducing organisms (asexually reproducing aren't isolated, but are still called species - like bacteria - they are defined by biochemical and morphological traits)

Answer 56

a species is a set of organisms adapted to a particular set of resources (niche) in the environment

Answer 57

species members have a common but unique set of anatomical features that distinguishes them from other species.

Answer 58

Species that are defined by a unique genetic feature

Answer 59

When 2 populations are unable to find mates, they will continue to separated from each other over time.

Answer 60

Before fertilization occurs

Answer 61

after fertilization

Answer 62

Because the male and female gametes never come into contact, an interspecific zygote (fertilized egg) never forms

Answer 63

1. Temporal isolation 2. Behavioral isolation 3. Mechanical isolation 4. habitat isolation

Answer 64

prezygotic barrier where similar species reproduce at different times Example: Eastern Spotted skunk mates late winter, birth late spring, Western Spotted Skunk mates September, birth late spring, delayed implantation

Answer 65

prezygotic barrier where similar species have distinctive courtship behaviors - prevents individuals from seeing members of other species as mates

Answer 66

prezygotic barrier where similar species have structural differences in their reproductive organs - size or other features prevent them from mating

Answer 67

prezygotic barrier where similar species in close proximity have distinct habitats within the system

Answer 68

1. reduced offspring viability- nearly all hybrids (two species mixed) dies in the embryonic stage 2. reduced hybrid fertility. - Can be born but are not able to reproduce as well as the parents. Gametes are abnormal Bull (2n=60) X bison (2n=60) female Better fertility than reverse cross, but few fertile males horse (2n = 64) X male donkey (2n=62) = mule male horse X female donkey = hinny males infertile, females fertility rare, especially in hinny

Answer 69

speciation that occurs when one population becomes geographical isolated from the rest of the species. a. ring species ( example - go around a mountain, split into two species, can't reproduce interspecies when they get back together). a ring species is a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations b. adaptive radiation - arriving in a new habitat and radiating into smaller habitats (Galapagos finches - beak evolved based on environmental stresses) c. ecological release: a particular species will expand into a particular niche if that niche is unoccupied (Porto Santo rabbits - no competition, became smaller than european rabbits and couldn't interbreed with them).

Answer 70

When a population forms a new species within the same geographical region as the parental species. Common in plants, difficult to demonstrate in nature. a. species isolate from each other as ecological release occurs followed by niche partitioning. b. . hybridization followed by allopolypoidy c. niche partitioning

Answer 71

the possession of more than two sets of chromosomes

Answer 72

sexual reproduction between individuals from different species

Answer 73

when polyploidy occurs in conjuction with hybridization.

Answer 74

Because the polyploid condition provides the homologous chromosome pairs necessary for synapsis (when homologous chromosome pairs come together) during meiosis. An interspecific hybrid produced by allopolyploidy can reproduce with itself (self-fertilize) or with a similar individual. But allopolyploids are reproductively isolated from both parents since gametes of the allopolyploid have a different number of chromosomes than either parent.

Answer 75

2n1 X 2n2: n1 + n2 n1n2 doubles to 2n1n2 e.g. 2n1 =14 X 2n2 = 16: n1=7 + n2=8 15, doubles to 2n3 = 30 New 2n3 can not cross with either parent population What does this mean? 2n1 and 2n2 are diploid parents n1 and n2 are the haploid gametes that normally combine combine. But they can't combine if there are 2 parent species, one with 2n1=14 and one with 2n2=16 (gametes of n1 =7 and n2=8) because they aren't homologous (they each have a different number). So they have to double first (n3=15) and then form the new diploid species 2n3=30

Answer 76

Robert MacArthur (1958), who became one of the nation's leading ecologists, found that warbler species divided their time differently among various parts of the spruce tree. 5 species: Cape May, Yellow-rumped, Black-throated Green, Blackburnian, and Bay-breasted Differed whether they fed at the top or bottom of the tree, and whether on the outside or inside, and when they fed and rested. They were not occupying the same niche, but were partitioned.

Answer 77

Dramatic changes that sometimes occur in evolution. Large phenotypic changes such as the appearance of wings with feathers during the evolution of birds.

Answer 78

Populations slowly diverge form one another by the gradual accumulation of adaptive characteristics within each population. These accumulate as a result of different selective pressure exerted by different environments.

Answer 79

First proposed by SJ Gould. Long periods of stasis (no evolution) punctuated (interrupted) by short periods of rapid speciation that are perhaps triggered by changes in the environment. Helps explain gaps in the fossil record because few transitional forms would occur with punctuated equilibrium.

Answer 80

No transitional forms of organisms. The starting points (ancestral species) and end points (new species) are present, but intermediate stages in evolution are missing. Traditionally explained by the incompleteness of the fossil record.

Answer 81

Gradualists think that stasis in the fossil record is a result of stabilizing selection. Stasis is deceptive because fossils do not revewl ass aspects of evolution ( only show external structure and skeleton, not physiology).

Answer 82

a. part of the debris cloud recoalesced b. early atmosphere - H2 - volcanoes produced CO, CO2, H2O, N2, NH3, CH4 - would expect much UV, lightening, volcanism, heat

Answer 83

5 steps in the origin (abiogenesis) 1. synthesis and accumulation - Creating the beginnings of the chains 2. small organics polymerize - Building the chains (probably RNA, not DNA) 3. polymer replication processes develop - Once this happens, they need to be able to replicate themselves 4. polymer aggregates formed with its own chemistry Package them in a bubble with their own chemistry inside vs that on the outside 5. true life forms evolved (prokaryotes) - They are able to heal themselves

Answer 84

Oparin and Haldane originate idea in 1920’s Miller-Urey proposed more UV added pre-biotic ingredients into flask

Answer 85

- early atmosphere probably more CO, CO2, N2 - early atmosphere constituents are in some measure speculative - lack of evidence requires - the experiment may actually support - evolution is based ultimately on natural selection - theorists claim that rocks and hot lava provided reaction surfaces

Answer 86

The end of a lineage - occurs when the last individual of a species dies. 99% of all species that ever lived on the earth are gone

Answer 87

- Permian Extinction (290 – 245 mil yr bp) = Evidence of Gondwana glaciation, mostly marine extinctions, 96% of all marines, 8 of 27 insect orders. Due to violent Siberian volcanism. - Cretaceous Extinction (65 mil yr bp) meteoric impact? All dinosaurs gone . Rapid radiation of mammals in 10 mil yrs. Was one of many other extinctions that were worse. 60% of all animals. NOT THE BIGGEST EXTINCTION EVENT. - Pleistocene Extinctions (30 – 10k yr bp) Glaciation and post-glaciation, human caused? Minor case - current extinction rates are 100x to 1000x normal background extinctions, drastic but sub-mass extinction rates. ( the Anthropocene?)

Answer 88

Continuous low level extinction of species

Answer 89

When species become extinct, their adaptive zones become vacant. consequently, those organisms still living are presented with new opportunities for adaptive radiation and can diverge to fill the unoccupied adaptive zones.

Answer 90

The evolution of many related species from one or a few ancestral species in a relatively short period of time. (Galapagos finches)

Answer 91

New ecological roles or ways of living that were not used by the ancestral organism. Ecological niche. Each zone can only be occupide by one group of organisms. A newly evolved species can take over an adaptive zone that is already occupied if the new species has competitively superior features (finches beaks).

Answer 92

Extinction produces empty adaptive zones, which are then available for adaptive radiation. For example, mammals had existed for millions of years before undergoing adaptive radiation, thought to have been triggered by the extinction of the dinosaurs. The original mammals were small animals that ate insects. Soon after the dinosaurs died, mammals diversified, like flying bats, running gazelles, burrowing moles, and swimming whales that all originated from the small insect-eating ancestors.

Answer 93

Because diversity is occurring at the family level. Macroevolution created dramatic changes (bird wings with feathers) They changes are so great that the new species possessing them are assigned to different genera or higher taxonomic categories (families).

Answer 94

variations of some structure that originally fulfilled one role, but changed in a way that was adaptive for another role. Bird feathers from scales (originally may have been for thermal insulation, but the preadapted primitive birds for flight). Also, middle ear bones in mammals from modified jaw bones of reptiles.

Answer 95

varied rates of growth for different parts of the body. The size of the head in newborns is large in proportion to the rest of the body. As a human grows, the torso, hands, and legs grow more rapidly than the head.

Answer 96

changes that would occur if a juvenile characteristic were retained in an adult.(Gill forms in a salamander)

Answer 97

- energetically speaking - 2nd Law of Thermodynamics without adequate selection mechanism - theory does not demonstrate how an RNA with enzymatic properties - theory provides a speculative scenario - based on random chance

Answer 98

- lipids and polypeptides can self assemble into microscopic spheres - spheres can grow and divide - membraned spheres would have to have housed replicating RNA

Answer 99

Microscopic spontaneously formed spherical aggregates of lipid molecules that are held together by electrostatic forces and that may have been precursors of cells. alcohol coacervates, but any liquid not dissolvable in another will produce them

Answer 100

- highly speculative | - never demonstrated to have happened

Answer 101

theory – fossils confirm existence of prokaryotes at around 3.5 bil yr; these evolved from co-ops.

Answer 102

evolutionary pathway is speculative jumps between co-ops and prokaryotes is huge Going from a particle to a package the presence of life does not insure a process is available making life from non life beware of “God of the Gaps” explanations If there is no process, it happened because of God, until we find what the process is, then God gets pushed out of the picture.

Answer 103

a. relative dating b. absolute dating - radiometric dating=Looking at proportions of radioactive mats in a rock in comparison to decomposition of products - half life = How long it takes for the rad. Mats to decay in nonrad. Mats. (half-life is the period of time required for one half of the atoms of a radioisotope to change into a different atom) 1. ^14C dating assumes 5730 yr half life 2. ^238U dating assumes 4.5 bil. Yr. halflife all ^206Pb is from ^238U 3. ^40K to^ 40Ar with 1.5 bil. yr. half life

Answer 104

imprints casts concretions mineralization

Answer 105

separation rates (2cm/yr at present), eventually disrupts ocean currents, climate. evidence that the continents have coalesced three times, at 1.5 bya, 600 mya, and 250 mya, will again in 250 mil yr. Pangaea created 250 mil yr ago, caused extinction of marine animals when oceans deepened, large interior continental area was probably harsh. fossil evidence suggests early contact with continents long separated

Answer 106

Permian - modern insects, mammal-like reptiles, extinction of many invertebrates Carboniferous - Forests, seed plants, reptiles, amphibians Devonian - Diversification of bony fishes, tetrapids and insects appear Silurian -diversification of early vascular plants Ordovician - Marine algae, colonization of land by diverse fungi, plants, and animals Cambrian - sudden explosion of diversity

Answer 107

Oldest fossils of eukaryotic cells | Diverse algae and soft bodies invertebrate animals

Answer 108

Origin of earth Oldest know rocks Oldest fossils of cells (prokaryotes) Concentration of atmospheric oxygen increases

Answer 109

a. initial sequence in common ancestor | b. Constant mutation rate

Answer 110

a. mitochondria DNA | b. RNA sequence genes (DNA)

Answer 111

Because amino acid sequences reflect changes . Macros can be functionally similar in two different types of organisms and be considered homologous if their subunit structure is similar.

Answer 112

agree in part with fossil record. The greater the similarity in amino acid, DNA or RNA sequences, the more closely organisms are thought to be related. The number of differences may reflect how much time has passed since the groups branched off from a common ancestor (monkeys, elephants, rhinos, and wolves have a common ancestor based on DNA as well as fossil evidence).

Answer 113

Taxonomy and Cladistics

Answer 114

- based on commonly shared characteristics (anatomy) - employ hierarchical classification - resemble phylogenic trees Reptiles and birds would be grouped separately because even though they share a common ancestor there are too many differences since the initial branching (adaptations that have occurred over time like feathers) Birds would group with mammals

Answer 115

Emphasizes phylogeny, focusing on when evolutionary lineages divided into different branches. - based largely on genetics - has revealed paraphyletic groups - strives to order monophyletic groups - cladograms represent Reptiles and birds would be grouped together because they have a common ancestor Mammals would group separately

Answer 116

hypotheses of decent, not without evidence

Answer 117

Oak tree separates (no seeds that are like the locust or bean). Locust tree can group with beans even thought it is a tree because of the seed structure

Answer 118

all with a common ancestor, but humans branch closer to chimps, then gorillas, orangutans, and gibbons

Answer 119

binomial nomenclature (Genus species) Genus always capitalized, whole thing either underlined or italicized.

Answer 120

Kingdom, Phylum, Class, Order, Family, Genus, Species | How to remember it: King Phillip Came Over From Germany Slowly

Answer 121

Prokaryotae, Protista, Fungi, Plantae, Animalia (proposed by Whitaker in 1969)

Answer 122

Algae, including multicellular forms, protozoa, water molds, slime molds

Answer 123

mushrooms and molds, decomposers

Answer 124

Species (they are the only one defined by their common gene pool, all taxons above this are artificial constructs designed by taxonomists)

Answer 125

a taxonomic grouping at any level

Answer 126

evolutionary history of organisms

Answer 127

evolved from a common ancestor. If you go far enough back in time, all taxa could share a common ancestor.

Answer 128

A paraphyletic group is a group of organisms that includes an ancestor but not all of its descendants. (like a group that consists of your parents and your siblings but not you)

Answer 129

A taxon containing a common ancestor and all the taxa descended from it

Answer 130

Many currently recognized taxa are actually polyphyletic, consisting of several evolutionary lines and not including a common ancestor. Taxonomists try to avoid this. Can think of it as cousins on a family tree (Nana and Pop-pop had Holly and I, I have you, Mel and Aaron, Holly has Ethan. you and Ethan are polyphyletic. But if you go back one step further, it becomes paraphyletic (we all get grouped back together with N & P)

Answer 131

The recent common ancestor of all the descendants in the tree is represented by the root. Descendant organisms are labeled at the tips of the phylogeny. A node indicates a divergence event and splits into two branches. A node also represents a common ancestor for the descendants that branch off of it.

Answer 132

traits that were present in an ancestral species and remained essentially unchanged (ability to nurse their young in mammals)

Answer 133

not present in an ancestral species because they evolved more recently. Example is three small bones in the middle ear. Allows the branch between mammals and reptiles. The evolution of the bones was a unique event and only mammals have these. But if we are only comparing mammals to each other, then the character is ancestral.

Answer 134

monophyletic

Answer 135

homologous

Answer 136

polyphyletic

Answer 137

Precambrian

Answer 138

Stromatolites

Answer 139

endosymbiont theory

Answer 140

Precambrian time

Answer 141

plate tectonics

First test Flashcards

Evolution, classification