chapters 8 and 9 - evolution

Question 1

How long has life existed on Earth

Answer 1

3.5 billion years

Question 2

Describe biogeography

Answer 2

The study of the distribution of organisms across habitats and how these have changed over geological time. Today’s separate land masses share fossils of the same extinct organisms showing a pattern of distribution and evidence of past life.

Question 3

State the theory of evolution

Answer 3

All organisms have developed from previous organisms and all living things have a common ancestor in some initial form of primitive life

Question 4

Define evolution

Answer 4

Evolution is the process of cumulative, heritable change in a population over many generations

Question 5

Define fossil

Answer 5

Fossils are any preserved trace left by an organism that lived long ago

Question 6

Define gene pool

Answer 6

The total collection of alleles within a population

Question 7

Define allele frequency

Answer 7

The proportion of an allele relative to the sum of all the alleles (both dominant and recessive)

Question 8

What is convergent evolution

Answer 8

The independent evolution of similar features (analogous strcutures) in species of different periods or epochs of time which were not present in the last common ancestor of those groups - occurs due to similar environmental pressures

Question 9

What is divergent evolution

Answer 9

The accumulation of differences between closely related populations within a species, some leading to speciation - occurs when two populations become separated by a geographic barrier and experience different selective pressures that cause adaptations

Question 10

Compare convergent and divergent evolution

Answer 10

Both are forms of evolution which cause adaptations based on selective pressures. Divergent evolution is when closely related populations of the same species adapt to become different from one another whereas in convergent evolution two different species adapt to become more similar due to undergoing the same environmental pressures.

Question 11

Define natural selection

Answer 11

Natural selection is a mechanism of evolution which occurs when selection pressures in the environemtn confer a selective advantage over a specific phenotupe to enhance its survival and reproduction - this leads to changes in the allele frequency in the gene pool of a population.

Question 12

Outline the steps of natural selection

Answer 12

1. Variation - individuals in a population differ from one another (show variation)
2. Overproduction - there are more individuals produced in a population than the environment can support causing environmental resources to be limited and not all individuals can survive to reproduce
3. Competition - environmental selection pressures favour organisms with more advantageous alleles/traits which may cause competition between individuals in the population and those with advantageous alleles may outcompete others
4. Higher reproductive rates - Individuals with the inheritable advantageous trait are more likely to survive, reproduce and have a higher reproductive rate than those who do not possess the allele
5. Heritability - Advantageous alleles are passed to offspring
6. Allele frequency change - Over consecutive generations, the frequency of advantageous alleles increases and the frequency of the disadvantageous trait decreases

Question 13

Compare natural selection and genetic drift

Answer 13

Natural selection and genetic drift both impact the allele frequency in a population’s gene pool but genetic drift is random whereas natural selection favours advantageous alleles and increases their frequency in the gene pool

Question 14

Compare natural selection and artificial selection

Answer 14

Artificial selection and natural both pass on advantageous traits and
allele frequencies change and may accumulate over generations. The major difference between
artificial selection and natural selection is that humans choose traits that are advantageous to
humans, whereas in natural selection, an environmental selection pressure selects a trait, and that trait
is beneficial for the survival of the organism.

Question 15

Define artificial selection

Answer 15

The intentional breeding/reproduction of individuals with desirable traits, resulting in changes in allele frequencies in gene pools over time and is achieved through selection of individuals with desirable traits to breed with.

Question 16

What is the purpose of selective breeding

Answer 16

The purpose of selective breeding is to produce favourable traits/outcomes in organisms for human benefit such as increased yield in crops, resistance to viruses or pesticides.

Question 17

Discuss the potential impact of selective breeding on allele frequency

Answer 17

Selective breeding can potentially create an allele frequency of 100% in a desirable trait, it can cause monocultures to occur where they may not have had they been left alone. This may be desirable as it could lead to a guaranteed increased yield in crops or guarantee any desirable trait in any organism.

Question 18

State one example of selective breeding in agriculture - what trait, what species, how this assists humans

Answer 18

One example of selective breeding in agriculture is the Bos taurus aka The Belgian Blue, a breed of cattle that has been bred for the meat industry through artificial
selection. The Belgian Blue’s physique comes from a naturally occurring ‘double muscling’
mutation. The mutation occurs in the myostatin gene (M), which codes for the protein myostatin
(‘myo’ = muscle, ‘statin’ = stop). Due to the mutation, muscle development is not regulated, resulting
in huge muscles.

Question 19

How do mutations introduce new alleles into a population

Answer 19

Point mutations in coding sections of DNA cause a different protein to be produced by the gene which creates an allele for that gene

Question 20

What is a homologous structure and name one example

Answer 20

Anatomical structures that are common to more than one species and were inherited from a common ancestor, but have different functions due to the species living in different environments under different selection pressures - an example is the forelimbs of vertebrates which have the same bones arranged in the same way even though they have developed for different functions (flying in birds vs mobility in humans)

Question 21

What is an analogous structure and name one example

Answer 21

Features of organisms that have the same function but not the same basic structure - similar environmental drivers can result in similar structures for example the eyes of octopi and humans which process light differently

Question 22

What is a selection pressure and name the three types

Answer 22

A selection pressure is an environmental factor that can be survived by those individuals in a population who possess a beneficial trait, but not others (this can contribute to changes in allele frequency in a population gene pool).

Resources - presence of food/prey/shelter
Abiotic - pH, temperature, water availability
Biotic - pathogens/diseases, predators

Question 23

Describe sexual selection

Answer 23

A mating process by male and female individuals for an inherited trait that assists in sex or in the winning of a mate - can be a counter to natural selection as some traits may be a disadvantage to survival e.g. peacock tails

Question 24

What is the difference between natural selection and sexual selection

Answer 24

Natural selection is caused by environmental pressures and favors traits that increase survival and reproduction whereas sexual selection is caused by individuals in a population and favors traits that increase an individual’s ability to attract and mate with a partner

Question 25

Define microevolution

Answer 25

Any small change in the gene pool of a population - the change is below species level

Question 26

Define macroevolution

Answer 26

An accumulation of micro-evolutionary changes over many generations and a long period of time - the change is above species level

Question 27

Define species

Answer 27

A group of organisms which are morphologically similar and are able to produce viable, fertile offspring and cannot breed with the individuals of another species to produce fertile offspring

Question 28

Define adaptive radiation

Answer 28

Organism diversify rapidly from an ancestral species into a multitude of new forms and occurs when a change in the environment makes new resources available, alters biotic interactions or opens new environmental niches

Question 29

What is allopatric speciation

Answer 29

When populations become physically separated through geographical isolation resulting in the disruption of gene flow and causing the populations to diverge (can be due to different environmental selection pressures or random processes like genetic drift)

Question 30

Describe the steps that lead to allopatric speciation

Answer 30

1. Subpopulations - a parent population divides into two or more sub-populations 2. Isolation by a physical barrier 3. No gene flow - due to the physical barrier, the two subpopulations are genetically isolated and there is no migration between the subpopulations 4. Different selection pressures - different environments apply different selection pressures and the subpopulations evolve independently 5. Natural selection - for each subpopulation different advantageous alleles are selected for resulting in different allele frequencies over generations 6. Genetic drift - genetic drift occurs independently, causing different alleles to be passed to offspring randomly 7. Two different species - small micro-evolutionary genetic differences over generations accumulate to become large differences until the two groups become two species

Question 31

What is the difference between macroevolution and microevolution - use an example to explain

Answer 31

Micro-evolution occurs below species level and refers to any small change in a populations gene pool whereas macro-evolution is the accumulation of micro-evolutions resulting in major evolutionary changes at a species level

Question 32

Define speciation

Answer 32

Speciation is the formation of a new species - it is the process of one species splitting into two or more species

Question 33

What are isolating mechanisms

Answer 33

Isolating mechanisms separate two subgroups in a population and prevent them producing fertile, viable offspring

Question 34

What are pre-reproductive isolating mechanisms

Answer 34

Pre-reproductive isolating mechanisms are biological or ecological mechanisms that prevent organisms from being able to interact or reproduce (temporal - breed at different times e.g. hour/day/season, behavioural - different courtship patterns, morphological - different reproductive structures)

Question 35

What are post-reproductive isolating mechanisms

Answer 35

Post-reproductive isolating mechanisms do not prevent mating but prevent young from being produced (gamete mortality - gamete does not survive, zygote mortality - zygote does not survive, hybrid sterility - adult offspring are formed but are infertile)

Question 36

What are the mechanisms of speciation

Answer 36

Allopatric speciation and sympatric speciation

Question 37

What is sympatric speciation

Answer 37

The evolution of two or more new species from a single population in the same space and occurs due to various pre and post zygotic isolation mechanisms (much less uncommon than allopatric speciation)

Question 38

How can reduced genetic diversity increase risk of extinction and give an example of this

Answer 38

Populations with reduced diversity face increased risk of extinction. When genetic diversity is reduced there is a smaller variety of alleles and phenotype options as the pressures from natural selection change, lowering the chance of survival of the population.

Question 39

Name and outline a strategy for maintaining/expanding genetic diversity

Answer 39

One strategy for maintaining/expanding genetic diversity is through assisted migration (thus assisted gene flow) to increase reproductive fitness. This introduces new alleles to the population which may provide advantageous alleles that can be passed down through natural selection and increases the population which can lower the chance of inbreeding (which lowers reproductive fitness and can lead to undesirable rare recessive alleles being expressed)

Question 40

Sequence the history of life on earth

Answer 40

1. Bacteria, eukaryotes, multicellur organisms 2. Jawless fish, jawed fish, land plants + anthropods, trees, land vertebrates 3. Reptiles and amphibians become dominant 4. Most life eliminated; surviving organisms diversify; dinosaurs dominate; first mammals 5. Flowering plants; arrival of marsupials in Australia; dinosaurs extinct; Ice age; humans

Question 41

Describe comparative genomics and explain how it is evidence for evolution

Answer 41

Comparative genomics is a field of biological research in which researchers use a variety of tools to compare the genome sequences of different species - the more similar in sequence the genes and genomes of two species are the more closely related they are

Question 42

Describe comparative biochemistry (studies of proteins) and explain how it is evidence for evolution

Answer 42

Comparative biochemistry is the study of different kinds of proteins (including enzymes) and their fundamental units - proteins and the alleles that encode them, are subject to the same mechanisms of evolution as the larger traits that individuals possess. A protein that is well suited to its function will be conserved, while other traits around it may evolve - proteins consist of long chains of amino acids and each proteins differs in the number type and sequence of amino acids: the number of differences is used to determine the relationship and relatedness between organisms

Question 43

Describe the fossil record and explain how it is evidence for evolution

Answer 43

The fossil record is made up of all the fossils that have been found, along with their relative ages. Scientists are able to compare

Question 44

Describe comparative anatomy and explain how it is evidence for evolution

Answer 44

Comparative anatomy is looking at the structures of organisms and understanding how different organisms can evolve to have different uses for the same structure (homologous structures) or have different structures for the same function (analogous). By comparing structures that have evolved to have different functions, by tracing back to the most recent ancestor with this structure scientists can identify the relationships between organisms and relatedness

Question 45

Describe embryology and explain how it is evidence for evolution

Answer 45

Embryology is the comparison of early stages of development of organisms. The embryos of different vertebrates are very similar and show features that are not present in adults suggesting that these vertebrates evolved from a common ancestor. For example, at one point in development, the embryos of humans and chickens have slits and arches in their neck which are similar to the gill slits and arches in fish but these do not develop into gills indicating common ancestry with later evolution along different pathways.

Question 46

Evaluate the reliability of comparative genomics and list examples of it

Answer 46

Comparative genomics is extremely reliable as the same genome can be compared numerous times to numerous organisms to make numerous conclusions. Essentially, in comparative genomics, all procedures can be repeated to increase the reliability of the result. One example of comparative genomics is the study of the relationship between the pink flamingo and the horned grebe showing a closer relationship than previously assumed based only on morphology.

Question 47

Evaluate the reliability of comparative biochemistry (study of proteins) and list examples of it

Answer 47

Comparative biochemistry is highly reliable because all procedures can be repeated and replicated to increase the reliability of results.

Question 48

Evaluate the reliability of the fossil record and list examples of it

Answer 48

The fossil record is unreliable, fossils need to be extremely well preserved from the moment of the organism's death meaning that we don't actually have very many fossils, and the ones we do have lend themselves to fossilisation anyway. There are also huge gaps in the fossil record because of this!! An example of this is Archeopteryx which is a fossil.

Question 49

How does bioinformatics play a part in genomic comparison and species relatedness

Answer 49

Bioinformatics is the digital storage, retrieval, organisation and analysis of an enormous volume of biological data (the combination of biology mathematics and computer science). Bioinformatics has advanced scientists knowledge of entire genomes of organisms which can then be compared to other organisms for the number and volume of differences to show relatedness and possible common ancestors.

Question 50

Define gene flow

Answer 50

The movement of alleles from one population to another

Question 51

How does immigration effect allele frequency

Answer 51

Immigration introduces new alleles to the population, altering the existing allele frequency by increasing the size of the gene pool.

Question 52

How does emigration effect allele frequency

Answer 52

Emigration removes alleles from the gene pool and makes it so every individual in the population now accounts for a larger percentage of the allele frequency and thus reduces the genetic diversity of that population

Question 53

How does reproduction rate effect allele frequency

Answer 53

High reproduction rate means the alleles of each individual in a population accounts for less of the allele frequency of the gene pool meaning that micro-evolutions will have less of an impact.

Question 54

How does genetic drift effect allele frequency

Answer 54

Causes a random, non-directional change in the allele frequency between generations and will have a larger effect on the allele frequency if the population is small

Question 55

How does the bottleneck effect, effect allele frequency

Answer 55

A population bottleneck is when there is a reduction in the size of a population, this means each individual's alleles account for more of the allele frequency of the gene pool. After a population bottleneck has occurred the allele frequency of successive generations generally will show very similar allele frequencies due to the smaller gene pool of the parent generations.

Question 56

How does the founder effect, effect allele frequency

Answer 56

The founder effect is an extreme example of genetic drift where a small population breaks away from a larger population (e.g. move to an island), the new population can have a different allele frequency from the original population and/or decreased genetic variation. If for example the allele frequency of the new population is 1 for a certain trait then all successive generations will inherit this trait - limiting genetic diversity.

Question 57

Define genetic drift

Answer 57

The random non-directional change in allele frequency between generations - occurs in all populations but is more important in small populations (individuals have a greater impact on allele frequencies since gene pool is smaller)

Question 58

How can transitional forms show the change of a species over time and use examples to explain

Answer 58

Transitional forms exhibit common traits found in both the ancestral form and the more modern species for example the dinosaur-bird Archaeopteryx which exhibited both reptilian (tail, claws, teeth) and avian (wishbone, feathers) features acting as evidence to suggest birds and reptiles share a common ancestor.

Question 59

List ways a species can be identified

Answer 59

Fossil dating, carbon dating and stratigraphy

Question 60

How do fossils form

Answer 60

1. Organic matter is quickly deposited and covered in sediments in an environment that lacks oxygen preventing decomposition 2. Minerals from sediment replace the natural bone/shell material, hardening the fossil 3. Organisms covered with sedimentary materials (e.g. mud), materials consolidate to form sedimentary rock 4. A long period of time passes

Question 61

What is the best environment for fossil formation

Answer 61

Alkaline environments are best due to the high pH allowing minerals like lime or iron oxide to be deposited in the pores of the bones and replace the decaying organic material to petrify it. Soft body fossils require acidic environments with low oxygen.

Question 62

What is stratigraphy

Answer 62

The study of layers of sediment and their order as an understanding of periods of time passing

Question 63

Define biological fitness

Answer 63

The capacity of an individual to survive and produce viable, fertile offspring