Chapter 9 - Mechanisms of evolution and speciation

Question 1

Theory of evolution

Answer 1

States all organisms have developed from previous organisms and that all living things have a common ancestor in some initial form of primitive life. Also states that all organisms are fundamentally similar because their chemistry was inherited from this very first organism

Question 2

Gene pool

Answer 2

Collection of all the alleles for all the genes in the reproducing members of the population at a given time. It is the genetic a reservoir from which a population can obtain its traits

Question 3

Hardy Weinberg equilibrium principle

Answer 3

States that allele frequencies in a population will remain constant in the absence of the four factors (mechanisms) that could change them. Four factors are mutation, natural selection, genetic drift and migration (enabling gene flow)

Question 4

Mutation

Answer 4

A permanent change in the DNA sequence of a gene, a source of new alleles in a populations gene pool. Can change one allele into another, and the net affect is a change in the frequency of an existing allele

Question 5

selection pressure

Answer 5

An abiotic or biotic environmental factor that enhances the survival and reproduction of those individuals in a population who posses a beneficial treat and reduces the survival and reproduction of those individuals without the trait

Question 6

Natural selection

Answer 6

Occurs when selection pressures in the environment confer a selective advantage on a specific phenotype that enhances it survival and reproduction. It is a process in which individuals that have certain inherited traits are more likely to survive and reproduce at higher rates than other individuals because of those traits. It can cause changes in a populations allele frequencies (gene pool) and therefore as a mechanism for evolution

Question 7

steps to natural selection

Answer 7

• variation: Individuals of a population have many characteristics that differ due to mutation
• Overproduction: Every species tends to produce more individuals than can survive to maturity
• Competition and survival of the fittest: Environmental selection pressures (Food availability, predators, disease) Favour those with more advantageous traits. Leads to competition between individuals and those with the advantageous trait outcompete those without
• Higher reproductive rate: Individuals with the inheritable advantages trait are more likely to survive, reproduce and have a higher reproductive rate and those to that do not possess the trait
• Heritability: advantageous allele passed onto offspring
• Allele frequencies change over generations: Over consecutive generations, the frequency of the advantageous trait increases and the frequency of the disadvantagous traits decrease. Over many generations and a relatively long time, advantageous allele can become fixed (frequency becomes 100%)

Question 8

accumulation

Answer 8

The process of alleles or traits gradually becoming more common over generations

Question 9

adaptive evolution

Answer 9

Changes in a population of organisms that make the population better adapted to its environment over time

Question 10

Artificial selection (selective breeding)

Answer 10

The intentional breeding or reproduction by humans of individuals with desirable traits, resulting in changes in Allele frequencies and gene pools over time. Traits are beneficial to humans. eg, Selective breeding of sheep for best quality meat, wool and size

Question 11

Traits that breeders have tried to incorporate into crop plants

Answer 11

• Improved quality (nutrition, flavour, beauty)
• Increased yield
• increased tolerance of environmental pressures
• resistance to viruses, fungi and bacteria
• increased tolerance to pests
• increased tolerance to herbicides
• longer storage

Question 12

Advantages of natural selection

Answer 12

• Slower growth rate, more time to adapt to changes in environment such as poor soil quality
• Higher genetic variation, less susceptible to changes in environment

Question 13

Advantages of artificial selection

Answer 13

• Usually faster growth rate

- Increase nutritional value, large yield, pasta resistant, drought resistant, disease resistant

Question 14

Natural vs artificial selection

Answer 14

• Natural: Occurs naturally without human interference, increases species chance of survival e.g. Galapagos finches
• Artificial: Human select desired traits and benefit humans, may not enhance survivability e.g. dogs, crops, cattle
• Both: Traits inherited from parents, results in changing allele frequency, change occurs over many generations

Question 15

Sexual selection

Answer 15

Selection process that occurs between males or females in a population for an inherited trait that assists in winning a mate. E.g. big antlers of a moose, tail of a peacock

Question 16

Sexual dimorphism

Answer 16

Different morphologies between males and females of species for example males are larger with many elaborate colours

Question 17

Genetic drift

Answer 17

A change in the gene pool of a population as a result of chance over time. Effects strongest in a small population. Occurs when a random, non-representative sample from the population produces the next generation and therefore overtime the proportion of an allele can drift up or down

Question 18

Why is genetic drift in large populations not noticeable overall

Answer 18

The randomness of inheritance of alleles is not noticeable because the proportion of alleles that are affected is a low

Question 19

Bottleneck affect

Answer 19

A random reduction in the size of population which can lead to a reduction in the gene pool because of the misrepresented allele proportions. Can occur when a catastrophic event or a period of adverse conditions drastically reduces the size of the population

Question 20

example of the bottleneck effect

Answer 20

Northern elephant seals have reduced genetic variation due to hunting. Hunting reduce their population size to a few is 20 individuals at the end of the 19 century. Since then, the population has rebounded to over 30,000 but their genes still carry evidence of the bottleneck. They have much less variation than a population of southern elephant seals that were not hunted

Question 21

founder effect

Answer 21

Random reduction in a population that occurs when a few individuals become isolated from a larger population and form new population that does not carry all the alleles that were present in the original population. New population carries an unrepresentative set of alleles. Reduces genetic diversity due to reduced number and diversity of founding individuals

Question 22

example of the founder effect

Answer 22

Amish community. Settled somewhere new and mixed very little with other populations. Around 200 people originally formed the community and at least one of them harboured a recessive allele for a disease which is now common among amish people

Question 23

Gene flow

Answer 23

The transfer of alleles that results from immigration, emigration and migration of individuals between populations

Question 24

example of gene flow

Answer 24

Indigenous Australians do not possess the B allele that results in B or AB type blood. Overall frequency of the allele is increasing with indigenous Australian population due to migration of Asians and Europeans into Australia and the genetic flow between these populations

Question 25

What are the four mechanisms for evolution

Answer 25

• mutation
• natural selection (natural, artificial, sexual selection)
• genetic drift (bottle neck and founder effects
• gene flow (migration)

Question 26

Tree of life

Answer 26

Collaborative project of biologist from around the world providing up-to-date information about biodiversity, the characteristics of different organisms and their evolutionary history (phylogeny)

Question 27

Micro evolution

Answer 27

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

Question 28

Macro evolution

Answer 28

The evolution of new groups of organisms comprising many related species through multiple speciation events. Includes adaptive radiation’s. Result of a series of speciation events

Question 29

Biological species concept

Answer 29

Definition of a species based on whether members can interbreed to produce fertile offspring

Question 30

Morphological species concept

Answer 30

Definition of a species using measurable anatomical criteria and characteristics

Question 31

speciation

Answer 31

The evolution of one or more new species from an ancestral species. The population is considered a new species when it can no longer interbreed with the ancestral species

Question 32

example of speciation

Answer 32

The tortoises on the Galapagos Islands originally came from the mainland population but had changed over time to become better suited to the environment islands. New species of giant tortoises were formed with the closest living relative the Chaco tortoise in Argentina

Question 33

What are the three broad processes that work together towards macro evolution

Answer 33

• micro evolution: Populations change over time as the gene pools accumulate small changes in response to natural selection.
• Speciation: eventually a population accumulates so many changes that a new species can be identified.
• Macro evolution: Rapid series of speciation events leads to the development of a whole collection of new species, genera or families.

Question 34

What are the mechanisms of speciation

Answer 34

Reproductive isolation, pre-reproductive isolating mechanisms and post reproductive isolating mechanisms

Question 35

Reproductive isolation

Answer 35

When a single population becomes two separate populations that are unable to interbreed due to physical, biological or behavioural barriers

Question 36

Adaptive radiation

Answer 36

The process by which a species rapidly diversifies into many taxa with differing adaptations. Triggered by reproductive barriers, changes in availability of resources, new challenges or opportunities. Is the type of divergent evolution

Question 37

Divergent evolution

Answer 37

Process where related species evolve new traits overtime after living in different habitats, becoming increasingly different from their common ancestor and from one another, giving rise to a new species

Question 38

Isolating mechanisms

Answer 38

Mechanism that prevents organisms from mating or producing offspring. Can operate before reproduction has occurred or after reproduction

Question 39

pre-reproductive isolating mechanisms

Answer 39

Mechanism that prevents organisms from being able to interact to reproduce. E.g. time mechanisms (different mating times), behavioural mechanisms (different courtship patterns), morphological mechanisms (different reproductive structures)

Question 40

post reproductive isolating mechanisms

Answer 40

Mechanism that prevents fertilisation occurring or an embryo developing into viable offspring if fertilisation does occur. E.g. gametes mortality (gamete does not survive), zygote mortality (zygote forms but does not survive), hybrid sterility (offspring formed but infertile)

Question 41

allopatric speciation

Answer 41

Speciation that occurs due to physical geographic isolation. Physical barriers including water, land or mountains due to continental drift, rising sea levels, climate change

Question 42

steps of allopatric speciation

Answer 42

• subpopulations: Parent population divides into two or more sub populations
• isolation by physical barrier: Physical barrier (mountain range, river, desert) separates and isolates sub populations
• no gene flow: Genetically isolated, no migration between sub populations
• different selection pressures: Different environments apply different selection pressures, to sub populations evolve independently from each other
• natural selection: Different advantages and alleles are selected for survival of the fittest, resulting in different allele frequencies over generations
• genetic drift: Occurs independently in sub populations, causing different alleles to be passed on to offspring
• two different species: Small micro evolutionary genetic differences over generations accumulate to become large differences until two groups become two different species. No longer able to interbreed to produce fertile offspring

Question 43

Sympatric speciation

Answer 43

Speciation that occurs without physical or geographic isolation e.g. feed on different things, choose mates based on different characteristics, mate at different times)

Question 44

Mass extinction

Answer 44

Extinction of many species of a relatively short period of time

Question 45

What was the largest mass extinction event on earth

Answer 45

The great dying, one of the most extensive periods of volcanic activity earth has ever seen. Close to wiping out life