Lecture 10-13

Question 1

What is a taxonomic rank?

Answer 1

The most specific unit of taxonomic classification (ex. Homo sapiens)

Question 2

What is a biological classification?

Answer 2

A way we try to classify individuals based on a set of characters

Question 3

What is speciation? What does it depend on?

Answer 3

The creation of new species

Dependant on limited or absent gene flow between populations
- If gene flow does occur between populations, they will remain genetically similar therefore they cannot become different species if they share the same genes

Question 4

What are the mechanisms of speciation?

Answer 4

Change in gene flow due to something cuasing a pop. to seperate
- can be caused by physical barriers or geographic conditions (mountains, rivers, deserts)
- physically isolated pop. rarely interbreed and are therefore characterized by the lack of gene flow
- since different courtship behaviours, different breeding seasons, different periods of activity (diurnal vs. nocturnal)

Mutation, genetic drift, natural selection (or a combination) act separately on each isolated pop.

Leads to different isolated populations

Question 5

Where did the variation that natural selection acts on come from?

Answer 5

Natural selection may select for different variations in traits (alleles) between populations that
- already existed when they separated
- newly arose from chance mutations

Question 6

What is a mutation?

Answer 6

Random change that happens when DNA is replicated

Most are NOT adaptive, but some create new characters (most mutations are bad, but occasionally good)

Question 7

What is genetic drift?

Answer 7

Based on probability, the frequency of different genes in a population can change over time, even when not under selection pressure
- since at each generation, each allele is passed on randomly

Occurs in small populations by change

Whole alleles (traits) may even be lost

The allele is not under strong envr. pressure

Question 8

What is the morphological species concept?

Answer 8

Two populations that have distinguishable phenotypic characteristics (e.g., physical appearance, internal anatomy) are classified as different species by this concept

In other words, things that look similar and of similar size, shape, function, likely to be more related to each other

Question 9

What is the use of the morphological species concept?

Answer 9

Examining the fossil record, especially when fossils are the only data available

Question 10

What are the limitations of the morphological species concept?

Answer 10

Oldest species concept –> sorting species by appearance is a very coarse-grained way of differentiating groups

Does not take modern genetics into account (e.g. how genes and other microevolutionary differences affect what individuals look like)

It is much more accurate to use ecological and molecular evidence to determine whether individuals are the same species

Question 11

What is the biological species concept?

Answer 11

Defines a species as members of populations that actually or potentially interbreed (mate with each other) in nature and produce offspring that are fertile (can also reproduce)

Question 12

What are the issues with the biological species concept?

Answer 12

Assumes sexual reproduction, but not all species reproduce sexually
- does not work for asexual species (including animals and plants)

Cannot be used in all scenarios where we would like to distinguish between species

We cannot test the ability to mate between every pair of species (not practical/ethical)

Question 13

What is the phylogenetic species concept?

Answer 13

Species are groups of individuals that share a unique common ancestor

Determined by showing that individuals share traits (e.g. morphological, now usually genetic) unique to that species

Causes them to cluster distinctly from other groups

Branching out is due to speciation events

When no subset share a unique common ancestor, or there are no distinct clusters of individuals –> conclude that pop. are members of the same species as they share one common ancestor

Question 14

What is allopatric speciation?

Answer 14

Speciated caused by geographic isolation of two different populations

Low gene flow can occur between populations but must be rare

Caused by barriers such as mountains, canyons, movement of plate tectonics (panama), oceans, etc.

This type of speciation is believed to be the primary speciation which takes place on island

Question 15

What is parapatric speciation?

Answer 15

Speciation when the ranges of two speciating populations are actually overlapping but gene flow is reduced

A contentious theory, not all evolutionary biologists believe that parapatric speciation can occur

Question 16

What are ways for parapatric speciation to occur?

Answer 16

New niches open
- population moves into new niche
- niche causes evolution in the new pop.
- eventually, enough different to speciate

Environment differs across a large range
- environmental differences –> differences in evolution
- pop. at the far edges become very different since not exchanging genes
- eventually, individuals in the middle either disappear or become one of the two populations

Question 17

What is sympatric speciation?

Answer 17

A species arises from within a range of overlapping with its origin species

Question 18

How is gene flow restricted to a sub-population from within a larger population in the context of sympatric speciation?

Answer 18

Reproductive isolation
- reproductive methods are incompatible
- restricting gene flow, even in completely overlapping populations

Could be due to different rituals, reproductive structures, chromosome duplications in plants
– often arise from mutations
- infertile hybrid offspring

Question 19

What are hybrids?

Answer 19

Organisms that we consider to be different species can interbreed, hybridize

Offspring are often sterile

However, some interbreeding can create a viable offspring which can survive and mature (hybrid speciation)

Question 20

What is the exception to the rarety of hydrid speciation?

Answer 20

Plants

Often hybrid offpsring are fertile, even if not many plants can propagate themselves
- Hybrids can spread without sexual reproduction

Question 21

What is despeciation?

Answer 21

When two species become one

Hybridization can cause distinct lineages to collapse into a single lineage with an admized mosaic genome

relatively rare

Gene flow between two different species can eliminate the distinction between those two species

Question 22

What are the two scales that characterize evolution?

Answer 22

Macroevolution: evoluation over geological time, mainly observed through fossils

Microevolution: evolution we can observe within a human generation, mainly observed through genomic work

Question 23

What is a trait?

Answer 23

Observable feature in the phenotype of an organism

Generally physical or physiological characteristics, but can also be considered behavioural in some instances

Examples: organ presence, body size, colour, live birth, migration, etc.

Question 24

How does trait evolution work?

Answer 24

Traits are generally linked to the genome (genes of the organism)

Randome mutation can create new or altered genes

Some will be expressed as new phenotypes

Natural selection acts on the phenotype

Question 25

What is the likelihood of a mutation?

Answer 25

Severe mutations adding completely novel traits are extremely unlikely Most evolutionary changes are slight modifications on existing traits But genes can be duplicated or repurposed

Question 26

What does gene duplication have to do with mutation?

Answer 26

Can have duplication of genes or large sections of a chromosome Duplicate copy mutates and acquires new function Major source of raw material for genes to evolve

Question 27

What is specialization?

Answer 27

A species losing generalized traits to become better adapted to a very specific habitat/niche

Question 28

How have orchids evolved into a specialized group?

Answer 28

Seeds have lost the ability to germinate by themselves - little to no stored energy Need to form a symbiosis with a mycorrhizal fungi to germinate and grow Saves energy for the orchid since little energy investment required for seeds Mycorrhizae likely only found in optimal habitats for orchid growth - way to ensure seeds are germinated in the best habitat

Question 29

Can a species regain a trait if it is lost through evolution?

Answer 29

Poor evidence for this in the fossil record, but we do find examples such as the viviparous lizard - some lay eggs some have live births - not all genes present in the genome are expressed, they are regulated --> expression can be turned on and off

Question 30

What is irreducible complexity?

Answer 30

Trait(s) whose function(s) have become so essential to life, losing them through evolution seems impossible example: mitochondria

Question 31

Why was the evolution of seeds in plants a key innovation?

Answer 31

First land plants reproduced mainly by spores Development of seeds allowed plants to reproduce away from water and experience dormancy Allowed greater provisioning and dispersal Vast majority of plants now reproduce by seed

Question 32

What is the island rule (or fosters rule?)

Answer 32

Species that evolved on islands typically get either larger or smaller than their mainland counterparts (trait evolution of body size)

Question 33

What is insular dwarfism?

Answer 33

Animals which are large on the mainland become smaller on an island Because islands have limited resources, smaller animals need less food Herbivores - larger size deters predators - few to no predators on island - larger size no longer selected for Carnivores - prey tends to be smaller on islands - larger size no longer needed

Question 34

What is insular gigantism?

Answer 34

Species which are small on the mainland tend to become large on islands Carnivores - often lack large carnivores on islands - new carnivores species can become larger to fill the niche of apex predator Herbivores - small herbivores stay small to escpae predation - if there are no efffective predators, they will become larger (selective pressure gone)

Question 35

How can we date evolution?

Answer 35

Molecular clock The background rate of mutation, often of "invisible) mutations (e.g. ones that don't change the phenotype) Compare the number of changes - more similar = recent divergence - more different = less recent

Question 36

What is gradual speciation?

Answer 36

Species arise slowly over time Many morphological intermediates - evolutionary steps between an ancestral species or trait and a species or trait seen today - example: there is evidence for gradual evolution of the eye Traits change slowly and gradually - example: creeps

Question 37

What are the issues with gradual speciation?

Answer 37

If intermediate forms are adaptive, why does evolution continue? Why doesn't evolution move towards stabilizing selection instead of changing traits over time?

Question 38

What is punctuated equilibrium?

Answer 38

Species diverge quickly After quick divergence, remain unchanged over long periods of time - stabilizing selection Single of very few mutations must occur in a short period of time (new mutations in offspring) Mutations must be severe enough to cause noticeable changes in the phenotype - but not so severe that the fitness of the organism is negatively impacted Less common than gradual speciation Must be reproductive or geographic isolation between the ancestral species and new species

Question 39

What can impact our evaluation of gradual speciation vs. punctuated equilibrium?

Answer 39

May be biased by an incomplete fossil record (missing many intermediate forms in the fossil record)

Question 40

Generally what conditions lead species to not change?

Answer 40

If habitats remain stable over time, species tend to remain stable (assuming genetic drift is not significant)

Question 41

What is adaptive radiation?

Answer 41

Rapid speciation event into a multitude of new forms Adaptive: - evolutionary changes shape traits allowing organisms to adapt to their envr and convey fitness advantages - when natural selection meets a particular ecological opportunity - often these species vary in their microhabitat or food sources Radiation: - seems to correlate with a sudden abundance of open niches

Question 42

What is an ecological niche?

Answer 42

The specific place a species holds in its biotic and abiotic envr. E..g. the physical space where it feeds/reproduces, etc. the role it plays in the food chain of its community and its interactions with other organisms No two species can hold exactly the same niche in the same envr. One outcompetes the other

Question 43

What are some aspects that define the niche of an organism?

Answer 43

Predators, elevation, ecosystem type, competitors, food source, nesting season

Question 44

What might cause an abundance of unfilled niches?

Answer 44

When old niches are cleared out - dispersal to new envr (island, lake) - extinction events When new features open up new niches - hard bodies - angiosperms When new niches are engineered/created

Question 45

What is an example of the emptying of niches?

Answer 45

End-Cretaceous Extinction Loss of dinosaurs = abundace of empty niches Led to incredible adaptive radation in mammal species Resulted in the domination of mammal species today

Question 46

Why did mammals recover and dinosaurs did not?

Answer 46

Small size --> fast reproduction rate Generalist habit --> could survive on a diverse range of foods Lead to mammal radiation

Question 47

What is an example of a new feature creating new niches?

Answer 47

Rapid emergence of new traits such as hard bodies, predation, eyes - Massive radiation of new animals during the Cambrian (Cambrian explosion) Adaptive radiation in Angiosperms

Question 48

Why did angiosperms experience extreme adaptive radiation and increase at the expense of all other plant groups (conifers)?

Answer 48

Coevolved with pollinators - flowers attracted pollinators - pollinators greatly improved pollen transmission - an insect can travel much farther than wind-dispersed pollen There was therefore the major diversification of angiosperm pollinators along with angiosperms - new pollination niches Decline in pollinators associated with other plant groups (such as conifers) - some switched to angiosperms

Question 49

Where did the first angiosperms arise?

Answer 49

In forests dominated by conifers However, angiosperms grow more rapidly than conifers - moreover, angiosperm litter neutralizes the soil and favours the envr that they grow better in (compared to conifers that like more acidic soil) Once dominant, angiosperms had changed the abiotic and biotic landscape to favour their own growth Conifers today are largely limited to colder areas where angiosperms cannot thrive due to short growing seasons

Question 50

What is convergent evolution?

Answer 50

Independent evolution of analogous traits (structures, functions, behaviours) in two or more lineages The trait in question is NOT present in the last common ancestor of both groups Evolved similarly because they occupy the same evolutionary niche

Question 51

What are examples of convergent evolution?

Answer 51

Flight has evolved in very diverse lineages (arthropods, birds, mammals, pterosuars) Venom injection arose separately in cobras and vipers, and in platupi hornets and scorpions

Question 52

What are examples of convergent evolution?

Answer 52

Flight has evolved in very diverse lineages (arthropods, birds, mammals, pterosuars) Venom injection arose separately in cobras and vipers, and in platupi hornets and scorpions Phylogeny of seed plants shows that alternative photosynthesis paths evolved independently many times in diverse lineages

Question 53

Carcinization definition

Answer 53

The urge to become a crab A crab like body-plan has arisen independtly 5+ times

Question 54

How do check the evidence for convergent evolution?

Answer 54

Map a trait onto a phylogeny Look for present of train in fossil ancestor - if trait is present in ancestors --> not convergent (however traits can be lost, do not need to be in all decedents)

Question 55

What is mimicry and is it an example of convergent evolution?

Answer 55

phenomenon characterized by the superficial resemblance of two or more organisms that are not closely related taxonomically - can evolved to look like smt noxious Yes, it is an example of convergent evolution For example, a non-toxic species evolving to resemble an unrelated toxic/dangerous one to deter predation

Question 56

What is parellel evolution?

Answer 56

Similar development of a trait in distcint species that are not closely related, but share a similar originial trait, in response to similar evolutionary pressure - expanded in similar niches Different from convergent in that ancestors shared the trait Example: placental mammals and marsupials (with pouches) --> each lineage developed similar forms on different continents after they diverged to fill similar niches

Question 57

What does the founder effect do to the founder population of an island?

Answer 57

Smaller than source population Contains only a subset of the genetics of the original population May also have harmful recessive founder mutations

Question 58

Why does the founder effect lead to faster evolution?

Answer 58

Due to small populations, there are fewer individuals and fewer genes overall in the gene pool Therefore, each individual gene counts for more of the overall gene frequency Mutations spread much more rapidly because a new mutation in a small gene pool makes a larger overall contribution to genetic diversity compared to a large population The greater the frequency of a gene in the gene pool, the greater chance it will be passed on in the pop. Also relates to genetic drift leading to bottleeck effect

Question 59

Where do we find the highest human genetic diversity in the world?

Answer 59

Africa - a greater proportion of rare allele in African populations (rare alleles are likely to be lost in founder population unless they become dominant) Europe is lower - greater proportion of deleterious mutations in European populations South America is the lowest

Question 60

What is sexual selection?

Answer 60

differential fitness that is not related to envr but to sexual process, example behaviour trait (such as a call) that attracts mate --> that trait will be under sexual selection The mate preferences of one, or both, sexes drives evolution In sexual selection, these maladapted traits may not be beneficial for the survival aspects of fitness - but seem to directly impact the reproduction of individuals

Question 61

What are primary sexual characteristics?

Answer 61

Characters required for reproduction such as ovaries Differences in the biological sexes directly related to reproduction (e.g. genitalia)

Question 62

What is secondary sexual characteristics?

Answer 62

Traits which are used in sexual selection, but are not required for sexual reproduction Can be for direct competition, or attractiveness, not behaviour though Examples: horns, pretty feathers

Question 63

What is sexual dimorphism?

Answer 63

Difference in appearance between males and females of the same speices

Question 64

What are the two types of sexual selection?

Answer 64

Intrasexual selection: within the same sex Epigamic (intersexual) selection: between sexes

Question 65

What is intrasexual selection?

Answer 65

Direct competition between two members of the same sex for the opposite sex Particularly strong in polygynous species (one male many females) Most often seen as male to male competition for female - female competing tends to not be for access to mates (rather territory, food) Female has limited (or no) choice in mate selection Males generally to not help care for offspring Examples: crabs, lions, gorillas

Question 66

What are common sexual dimorphism patterns in intrasexual selection?

Answer 66

Larger males than females Males have sexual ornaments used primarly for fighting other males (antlers, fighting spurs) Males similar colour to females

Question 67

What is epigamic (intersexual) selection?

Answer 67

Selective pressure from the member of one sex having complete choice over a mate of the opposite sex - display or other courtship to attract members of the opposite sex Most common type of sexual selection in species where both individuals help raise the offspring (but not required) - also "monogamous" pairs Most common type of epigamic seleciton is female of the species having primary choice in mates - male choice does exist, but much rarer

Question 68

What are common sexual dimorphism patterns in epigamic (intersexual) selection where males do not stay to help raise the offspring?

Answer 68

Males are often much more colourful than females (extreme sexual ornamentation) Females are often larger than males, or of a similar size

Question 69

What are common sexual dimorphism patterns in epigamic (intersexual) selection where males help raise the offspring?

Answer 69

Both sexes are often the same colour and size

Question 70

Why is female choice much more common?

Answer 70

Females invest more energy and resources --> bear the cost of reproduction - eggs are high energy investment, fixed number - pregnancy is energy intensive - reproductive success comes from breeding with the best male (helps ensure offspring are as fit as possible) - costly to choose poor mate Males - sperm: low input, high output - reproduction success comes from mating with as many females as possible - many mates = the male can afford to select a suboptimal mate

Question 71

What is the Bateman's Principle?

Answer 71

The sex which invests the most in producing offspring will become a limiting resource over which the other sex competes Implies the male can be the sex which invests the most

Question 72

Is male competition in epigamic selection possible?

Answer 72

Yes, though any system where mate choice exists is considered primarily epigamic

Question 73

Does the development of extreme sexual dimorphism impact fitness?

Answer 73

Yes, math models have shown that is actually decreases overall fitness Trade-off with survival for the male

Question 74

What are the 4 aspects of the Fisherian Runaway Selection Hypothesis?

Answer 74

Female prefer a secondary sexual characteristic Female selects that mate, then passes that secondary character to her male offspring She also passes on a genetic trait in her daughters to desire that secondary sexual characteristic Creates a positive feedback, increases the desirability and extreme nature of the character over generations

Question 75

What is the Sexy Son Hypothesis?

Answer 75

Females choose attractive mates because it means that their own male offspring will be better able to attract mates

Question 76

What is the handicap hypothesis?

Answer 76

Extreme secondary sexual characteristics - indicate to the opposite sex that the individual can afford to waste resources on developing the secondary sexual characteristic Effectively, the individual can "handicap" itself, and ye still survive - therefore it is a good choice for a mate

Question 77

What leads to reproductive isolation?

Answer 77

More elaborate sexual practices and structures Taxonomic groups with the greatest amount of sexual dimorphism generally also have the largest species diversity (presumably from more speciation)

Question 78

What is coevolution

Answer 78

Also known as reciprocal evolution Where two or more species impact each other's evolution

Question 79

What is the difference between natural selection vs. coevolution?

Answer 79

Natural selection refers to the broad changes in phenotypes in response to envr conditions (abiotic and biotic) On the other hand, coevolution refers to when a small number of traits/genes in one species directly impact the evolution of a second suite of traits/genes in another species

Question 80

What is symmetrical arms race?

Answer 80

Selection pressures are identical on two species Two species whose interactions result in them co-evolving the same trait Ex. Only the tallest trees receive full sunlight in a mature forest - Sunlight: symmetrical selection pressure on all tree species - Different trees evolving the same trait: increased height - A tree is only tall because the next tree threatens to overshadow it

Question 81

What is asymmetrical arms race?

Answer 81

Contrasting selection pressures Both species are co-evolving, however the selection pressure acting on the two species is different Ex. cheetah and gazelle - cheetah runs faster but can only maintain for a short distance (evolved traits for hunting: speed and stealth) - gazelle runs less fast but can run longer due to blood being cooled before reaching the brain (gazelle evolved DIFFERENT traits for evading capture: endurance and evasion) --> coevolution

Question 82

Symbiosis definition

Answer 82

A close and prolonged interaction between organisms of different species Can be beneficial to both partners, neutral to one partner or harmful to one partner

Question 83

What is mutualism

Answer 83

Interactions between two different species mutually benefit each other Two types: 1) Obligate mutualism: - two species must co-operate in order for both to survive - the survival of one species depends on the survival of the other - Ex. fig and wasp, corals 2) Facultative mutualism: - both species derive benefit from each other, but one would survive if the other went extinct - Ex. tarantula-frog

Question 84

What is the current hypothesis for the tarantula-frog facultative mutualism?

Answer 84

Tarantula protects frog from other predators Frog protects the tarantula eggs since it is specialized in eating ants (ants are the primary predator of tarantula eggs)

Question 85

What are the pros and cons of obligate mutualism?

Answer 85

Pros: outsourcing protection, food, energy, etc. Cons: extra vulnerability of relying on another species

Question 86

What is parasitism?

Answer 86

Interaction between two different species where one benefits at the expense of the other Highly destructive, since the parasite is living at the expense of the other species Generally very finely tuned to preserve the life of the host or at least conserve the host species - the parasite needs the host to survive since it depends on the host to complete its lifecycle

Question 87

What happens when a parasite kills large numbers of the host?

Answer 87

Usually a novel mutation is found in the parasite which throws off the careful host/parasite balance Often after time, the host will evolve a better defense to the new mutation, and equilibrium will be restored --> the parasite may even evolve to be less virulent

Question 88

Myxomatosis

Answer 88

Myxomatosis virus killed 99.8% of rabbits in Australia Within several years, the virus became less virulent There was a strong selection for rabbit immunity --> selection for strains that didn't kill all and quikcly Therefore, rabbits survived longer and disease transmission was enhanced

Question 89

Brood parasites cuckoos

Answer 89

Obligate brood parasite (cuckoo) doesn't raise own offspring, relies on birds of other species to raise its offspring Will find nests of other bird species, and lay its own eggs in the nest When the cuckoo eggs hatch, the babies will push the other eggs out of the nest - ensures that only cuckoo offspring is raised The host can sometimes identify the cuckoo egg before it hatches - will push the cuckoo egg out of the nest There is a continuous evolutionary arms race betweem the cuckoo finch and its host - Cuckoo eggs closely resembling the host the host evolves a diversity of egg patterns to try to distinguish its eggs from the cuckoo - if either species were to succeed completely, the other would become extinct