Evolution Flashcards

Question

Reading the Fossil Record

Answer 1

•at first scientists thought that fossils were just trapped organisms, then there were some observations they could not explain, fossils appeared to be of unusual or unknown organisms, or organisms that are no longer alive, there are no fossils of current living species •fossils are buried very deep, often below the earth’s surface, fossils are found in unexpected places (e.g. sea life fossils are found in mountains or present-day deserts)

Answer 2

•these fossil questions intrigued scientists who wanted to know more about them •the study of fossils to learn about prehistoric life emerged- paleontology, around this time geology, the study of Earth’s physical structure emerged as well, two scientists provided a wealth of new evidence on how species of Earth might’ve changed over time (Georges Cuvier & Charles Lyell)

Answer 3

•palaeontologist that discovered fossils of simple organisms were found at all fossil depths, fossils of more complex organisms were only found in shallower depths, in younger rock, these shallow depth fossils resembled living species, some rock layers contained fossils of species that did NOT occur in the layers above or below them

Answer 4

•although there was a clear pattern of change from layer-to-layer Cuvier proposed the theory of Catastrophism •rather than life evolving he felt that global catastrophes like floods caused extinction then a new set of species replaced the old ones •Cuvier’s theory accounted for the different species in each layer but not how they became progressively more complex

Answer 5

•Lyell came to the opposite conclusion of Cuvier, he put the following principals of Uniformitarianism in his book Principals of Biology •Earth has been changed in the past by the same processes that are happening now, geological change is slow and gradual, natural laws that influence these changes are constant and they were operating in the past, the same way they are today •although Lyell’s ideas were radical, he was right, earth was very old and mountain ranges were formed by extremely slow processes and gorges by very slow erosion

Answer 6

•by the 19th century there was growing evidence that Earth was ancient and that species might be evolving •the mechanisms for this could not yet be explained •the search for this mechanism became the life’s work of a young man named Charles Darwin

Answer 7

•the change to a population over time •theory: an explanation of scientific phenomena that is based on observation, experimentation, and reasoning: scientific research •theories are redefined or confirmed by extensive research from many independent sources, the strength of a theory depends on the amount of research that confirms it

Answer 8

•born in 1809, son of a British physician, he dropped out of med school, graduated with a BA from Cambridge university in 1831 and became a naturalist -> collected and studied specimens •in 1831 he took a job on a ship, the HMS Beagle which was a survey ship on a 5 year mission around the world •during this time he took many observations and began to see that organisms change over time

Answer 9

•evolution had been accepted throughout the scientific community for a long time before Darwin. •The mechanism for evolution however wasn’t understood, modern genetics had not yet been discovered •Darwin did not understand the concept of genes, mutations, etc, yet ideas of inheritance and populations were understood and he based his theory on these findings

Answer 10

•Gregor Mendel- 1866, provided a mechanism to explain how genes were passed down •Watson & Crick’s Model of DNA – 1953, presented the double helix structure •The Human Genome Project – 2003, determined the sequences of chemical base pairs that make up human DNA

Answer 11

•Variation- the differences between members of a population •Competition- the struggle for resources with other individuals with similar needs for the same or similar resources •Adaptation- an inherited trait that benefits an organism •Fitness- a measure of an individual's ability to pass on his/her traits, the ability to survive and reproduce in a specific environment

Answer 12

•all species are related by a common ancestral organism, over long periods of time (millions of years), populations that descended from this common ancestor changed, (accumulated different modifications) in order to survive in their environment (because they had spread in different habitats) •As a result, these population types became: different from their ancestral type and different from other descendent population (a common ancestor gives rise to 2 new species, which then give rise to 2 species each, you end up with 6 species from a common ancestor)

Answer 13

Population Growth- limited by natural hindrances to growth, many factors prevent populations from growing, and many individuals in a population must struggle to survive (and many don’t make it) (e.g., resources such as food and shelter support only a limited number of organisms) Selective Breeding- creates change to domesticated plants and animals, humans choose to allow only those individuals with desirable traits to breed, so only desirable traits get passed on to the next generation, and less desirable traits are eliminated, this accounts for the many different domesticated breeds that exist today

Answer 14

•after Darwin read Lyell’s Principle of Geology he realized around 1836, that new species could arise from an ancestral form by the gradual accumulation of adaptions to a different environment •in 1840, Natural Selection as the means of evolution -> wrote a long essay •in 1858, Alfred Wallace (1823-1913) sent Darwin a manuscript *proposed Theory of Natural Selection, identical to Darwin! +Lyell presented the paper at a conference •in 1859, Darwin finally completed “The Origin of Species by means of Natural Selection” and given the credit for the work •Darwin’s Theory of Evolution was a means to explain the diversity of life on Earth and how all organisms are related to one another and to the environment in which they live •it addressed the issues of Biology: 1. Great diversity of organisma 2. Their origins and relationships 3. Similarities and differences 4. Geographic distributions 5. Adaption to surrounding environment

Answer 15

•1. Species were not created in their present forms but had evolved from ancestral species. •2. Proposed a mechanism for evolution •Natural selection- a population of organisms can change over time as a result of individuals with certain heritable traits leaving more offspring than other individuals •this is due to •i) Struggle for existence- direct competition among individuals within and outside of population •ii) Trait Heritability - variation and differences among members of the same species can suit the environment and increase fitness •iii) Survival of the fittest- only those that can cope will survive AND this is dependent upon environment

Answer 16

•structures in different species that share a common ancestral origin but may serve different functions •similar structure, different function •evidence of divergent evolution (e.g., forelimbs of humans, bats, and whales (used for different purposes like grasping, flying, and swimming)) •also share homologous developmental processes

Answer 17

•structures in different species that perform similar functions but do not share a common ancestral origin •similar function, different structure •evidence of convergent evolution (e.g., wings of birds, bats, and insects (adapted for flying but evolved independently))

Answer 18

•structures in an organism that have lost most or all of their original function through evolution (e.g., pelvic bones in whales: evidence of terrestrial ancestry) •evidence of evolutionary history •shows adaptation to changing environments

Answer 19

•unexpected or unusual physical features in organisms, often resulting from evolutionary quirks or adaptations (e.g., Giraffe's laryngeal nerve: loops down the neck unnecessarily due to evolutionary constraints) •highlights the complexity and imperfections of evolution •reflects survival-driven changes over time

Answer 20

•resource limitation: scarcity drives competition •survival of the fittest: stronger or better-adapted individuals have an advantage •population regulation: Helps maintain balance and prevents overpopulation •evolutionary pressure: Promotes adaptations to improve survival and resource use

Answer 21

•since Darwin, genetics has allowed scientists to uncover the mechanism of heredity and the source of variation •geology has advanced allowing us to interpret the fossil record extensively •these advances have allowed us to confirm Darwin’s theory and further understand new evidences

Answer 22

•at first scientists thought that fossils were just trapped organisms •then there were some observations they could not explain fossils appeared to be of unusual or unknown organisms, or organisms that are no longer alive, there are no fossils of current living species, are buried very deep, often below the earth’s surface, are found in unexpected places (e.g., sea life fossils are found in mountains or present-day deserts)

Answer 23

•these fossil questions intrigued scientists who wanted to know more about them •the study of fossils to learn about prehistoric life emerged- paleontology •around this time geology, the study of Earth’s physical structure emerged as well •two scientists provided a wealth of new evidence on how species of Earth might’ve changed over time

Answer 24

•it wasn’t until the twentieth century that new sciences like paleontology and geology cast doubt that the earth was young… they used to believe the earth was 10 000 years old •also doubt that current organisms were always in that •modern geology, physics and astronomy all conclude that the earth is about 4.5 billion years old

Answer 25

•palaeontologists can now use radioisotopes to date rocks very precisely •radioisotopes = atoms that undergo radioactive decay at a constant rate

Answer 26

•genetics and other fields of biology combine to form the modern evolutionary synthesis which forms the basis for all work in evolutionary biology •today scientists discuss changes in the gene pool of a species over time vs changes in inherited traits of a species over time that Darwin described •gene pool= the alleles in a species or population •Individuals vary in their traits because they inherit different combinations of alleles •Natural selection acts to favour some genetic combinations over others

Answer 27

•all species have variation due to different combinations of the many alleles that are present in the population •sexual reproduction recombines these alleles and produces an almost unlimited number of combinations of the varied gamete cells (due to meiosis) •new or altered traits can arise from mutations that are naturally selected •mutations are a change in the genetic DNA -> switched, lost, new inserts •duplication of genes can also occur during crossing over in meiosis

Answer 28

•deletions often result in a low chance of survival •extra info can result in viable genes •scientists studied the gene responsible for the production of amylase which acts on starch– people of Japanese descent with high starch diets had multiple copies of the gene while people in the Amazon rainforest whose diet was low in starch had no extra genes. •this shows how a mutation became beneficial for the Japanese population

Answer 29

•when DNA is replicated the danger rate is less than one mutation in a million DNA bases •organisms have genomes consisting of millions and billions of DNA bases + populations have millions of individuals •some studies suggest that humans have mutation rates averaging 20 or more per individual •even if the mutations are neutral that means that our population is carrying over 100 billion genetic mutations

Answer 30

•closely related species share many homologous features such as the arrangement of bones because they share a common ancestor. •similarly they share homologous genes •these genes mutate and evolve over time •this provides evidence of relatedness between species

Answer 31

•are genes that have undergone mutations and no longer serve a useful purpose •like vestigial anatomical features (e.g., dolphins breathe through their noses but don’t need a sense of smell. Most mammals use 1000 olfactory receptors, dolphins have 1000 but only use 200) •Pseudogenes are found in virtually all species

Answer 32

•over the last 100 years, many important fossil discoveries have been made •they have enhanced our understanding of evolution •fossils and their distribution provided Darwin with important evidence for evolution •today the study of biogeography and plate tectonics and continental drift helps explain how some species ended up in certain areas •species distribution is captured in the fossil record •Fossil records support the theory of evolution •modern biology supports evolution through molecular genetics and geology as well •this has allowed us to understand the source of variation within species

Answer 33

•evolution happens when natural selection acts on the genetic probability within populations •genetic variation arises by chance through mutations and recombination •natural selection does NOT occur by chance •the environment favours certain individuals over others

Answer 34

•Darwin was hesitant to publish, even after he read Thomas Malthus “Principles of Populations” •he knew from his readings that populations are affected by natural hinderances to growth •factors such as disease, famine and drought prevent populations from growing and many individuals in a population must struggle to survive AND many don’t make it •Darwin proposed that this struggle for survival could result in the selecting of specific traits

Answer 35

•the environment is constantly changing •natural selection operates to enable the organisms to maintain their state of adaption (not to improve it) •for a species to remain in a constantly changing environment, it must have enough of the right kind of heritable variation to change along with the environment •if genetic variation is inadequate the species will go extinct

Answer 36

• is synonymous with natural selection •natural selection is the driving force of evolution where only the fittest survive to reproduce again and pass on their genes

Answer 37

•this is a good example of how a mutation and natural selection can lead to a change in one population •it is a single base mutation in DNA coding for hemoglobin •individuals who are heterozygous for the allele are resistant to malaria •if you are resistant to malaria, you live to reproduce and pass this mutation on •the population changes and over time the frequency of the allele increases

Answer 38

•Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic •the increasing prevalence of antibiotic-resistant bacteria is due to the overuse of antibiotics via incorrect diagnosis, unnecessary perscriptions, improper use of antibiotics by patients and the use of antibiotics as livestock food additives

Answer 39

•selective pressures can be high or low •they can result from any number of abiotic or biotic availability or predators– even your choice of mate •these selective pressures can result in different patterns of natural selection

Answer 40

•the most common form of selection •once a species becomes adapted to its environment, selective pressures maintain their evolved features and traits •occurs when the most common phenotypes within a population are favoured by the environment

Answer 41

•when the environment favours individuals with more extreme variations of a trait •when an organism migrates to a new environment, or when its habitat changes, it will encounter new forces of natural selection •may result in an observable change in a population (e.g., pesticide resistance in insects, decreasing size of pink salmon)

Answer 42

•favours individuals with variations at opposite extremes of a trait over individuals with intermediate variations. •sometimes, environmental conditions may favour more than one phenotype •Phenotype: the set of observable characteristics of an individual (e.g., African black bellied seed-cracker finches)

Answer 43

•random changes in allele frequencies within a population over generations, especially in small populations •Random Effect: Changes are not due to natural selection •Significant in Small Populations: The smaller the population, the larger the impact •Can Lead to Fixation or Loss of Alleles: Certain alleles can become dominant or disappear entirely by chance

Answer 44

•a sharp reduction in population size due to a sudden environmental event (e.g., natural disasters, habitat destruction, disease) •results in reduced genetic diversity and altered allele frequencies in the surviving population 1.Random Survival: Survival is often unrelated to genetic traits, making it a stochastic process 2.Loss of Genetic Variation: Many alleles may be lost, leaving the population with less genetic diversity 3.Potential for Inbreeding: Smaller populations are more prone to inbreeding, which can lead to an increased prevalence of harmful trait

Answer 45

1.The founder effect occurs when a small group of individuals establishes a new population that is isolated from the original group 2.This small "founding" population carries only a fraction of the genetic diversity of the original population 3.Reduced Genetic Variation: The new population may have less genetic diversity compared to the original population 4.Allele Frequency Shifts: Certain alleles may become more common purely by chance, while others may be lost entirely 5.Increased Genetic Drift: Small population size amplifies the impact of genetic drift, further altering allele frequencies over time

Answer 46

•in large populations in which only random chance is at work, allele frequencies are expected to remain constant from generation to generation •in an environment where no selective pressures are present

Answer 47

•there are 5 assumptions of the Hardy-Weinberg Equilibrium: 1)No Natural Selection 2)No Mutation 3)No Migration 4)A Large Population 5)Random Mating Occurs

Answer 48

•two dominant alleles (GG)

Answer 49

•one dominant and one recessive allele (Gg)

Answer 50

•two recessive alleles (gg)

Answer 51

•the observable expression of an individual's genotype is called their phenotype. A person's phenotype is the result of the interaction between their genotype and their environment

Answer 52

•a genotype is the genetic makeup of an organism or individual, which is determined by the DNA sequence at a specific location in the genome

Answer 53

1) p + q = 1 2) p2 + 2pq + q2 =1

Answer 54

•Tracking Genetic Disorders: Helps estimate carrier frequencies in populations (e.g., cystic fibrosis) •Understanding Evolutionary Forces: Detects when populations deviate from equilibrium due to mutation, selection, or drift •Conservation Biology: Guides efforts to preserve genetic diversity in small populations

Answer 55

•Mutation: Introduces new alleles into the population •Natural Selection: Changes allele frequencies based on survival and reproduction •Genetic Drift: Random changes in small populations •Gene Flow: Movement of alleles between populations •Non-Random Mating: Increases homozygosity or heterozygosity

Answer 56

•the relatively rapid evolution of a single species into many new species, filling a variety of formerly empty ecological niches (e.g., the Galapagos Finches)

Answer 57

•when two or more species evolve from a common ancestor, becoming increasingly different over time •driven by adaptation to different environments or niches •leads to homologous structures (similar structures with different functions, e.g., forelimbs of vertebrates) (e.g., humans and apes)

Answer 58

•when unrelated species evolve similar traits due to similar environmental pressures •results in analogous structures (different structures with similar functions, e.g., wings of bats and insects)

Answer 59

•occurs when two or more species influence each other’s evolution through close ecological interactions (e.g., Brazil nut trees and the agouti)

Answer 60

•is large scale evolutionary changes including the formation of new species and new taxa •Taxa: a taxonomic group of any rank, such as a species, family, or class (e.g.,Reptilia, Mammalia)

Answer 61

•Cladograms are used to illustrate the evolutionary relationships or phylogeny of different groups of species of organisms •by examining a cladogram, one can infer what groups are more closely related and the general sequence of events that gave rise to each group (e.g., birds are more closely related to dinosaurs than mammals) •Phylogeny: the evolutionary history of a group of organisms, and is often represented as a phylogenetic tree

Answer 62

•a cladogram is a diagram that displays the relationship between characteristics of living organisms. It contains branches sorted by traits such as bone structure, number of wings, or petal type •a phylogenetic tree is a diagram that displays genetic relationships.

Answer 63

•Phyletic gradualism- evolution occurs by the gradual accumulation of small changes. The intermediate stages of evolution not represented by fossils merely testifies to the incompleteness of the fossil record •Punctuated Equilibrium- evolutionary history consists of geologically long periods of stasis with little or no evolution, interrupted or "punctuated" by geologically short periods of rapid evolution

Answer 64

•we now know after completing the fossil record that evolution is gradual •we know this because of transitional forms. These are species that are the intermediate form between two species in a direct line of descent

Answer 65

•the process through which new species arise from existing species •it explains the diversity of life on Earth •Allopatric and Sympatric Speciation

Answer 66

•a group of organisms that can interbreed and produce fertile offspring •reproductive isolation is crucial for defining species

Answer 67

•Prezygotic Barriers: Prevent mating or fertilization (e.g., temporal isolation, behavioral isolation) •Postzygotic Barriers: Reduce viability or fertility of hybrid offspring (e.g., hybrid sterility)

Answer 68

•occurs when populations are separated by a physical barrier (e.g., mountains, rivers) •Geographic Separation isolates populations •Independent Evolution due to mutations, natural selection, and genetic drift •Reproductive Isolation develops over time (e.g., Darwin’s finches on the Galápagos Islands)

Answer 69

•occurs within the same geographic area •Polyploidy: Common in plants where chromosome duplication creates reproductive isolation •Behavioral or Ecological Isolation: Changes in mating preferences or resource use (e.g., Apple maggot flies that shifted from hawthorn to apple trees)

Answer 70

•Genetic Variation: Provides raw material for evolution •Natural Selection: Drives divergence between populations •Genetic Drift: Random changes in small populations •Environmental Changes: Create new selective pressures

Answer 71

•Habitat Fragmentation: Creates opportunities for allopatric speciation •Pollution: Can drive rapid changes in some species •Introduction of Invasive Species: Disrupts existing ecosystems •Conservation Efforts: Aim to preserve biodiversity and prevent extinctions