a4.1 (natural selection)

Question 1

define speciation

Answer 1

the process by which a population of one species diverges to become two distinct species

Question 2

allopatric speciation vs sympatric speciation

Answer 2

allo = populations become geographically separated
symp = can occur within the same geographic area

Question 3

3 steps to allopatric speciation

Answer 3

1. populations begin to be geographically separated (eg. uplift of land, the movement of a glacier, or formation of a body of water)
2. two populations independently evolve, accumulating different gene mutations and being subjected to different selective pressures
3. the populations evolve to the point of not being able to interbreed and exchange genes. they are now separate species according to the biological species concept

Question 4

example of allopatric speciation - panama and atlantic porkfish

Answer 4

panama and atlantic porkfish being separated by the isthmus of panama (the narrow strip of land above coloumbia and below costa rica formed by tectonic plate movement)

Question 5

example of allopatric speciation - squirrels

Answer 5

kaibab (north of canyon) and abert’s (south of canyon, original species) squirrel in the colorado plateau in the grand canyon

Question 6

how are groups separated sympatric speciation

Answer 6

groups are separated by differences in behavior or timing of life cycles

Question 7

define polyploidy

Answer 7

another cause of sympatric speciation that is common in plants

Question 8

when does behavioural isolation occur? & examples of how this may occur

Answer 8

when a behavior prevents reproduction between individuals.

for example, different individuals may have different preferences for breeding calls, mating dances, pheromones, or feeding locations within a habitat.

Question 9

example of behavioural sympatric speciation - cichlid
(2 species names & changes)

Answer 9

littoral vs benthic cichlid fish (tanzania)
body color, shape, size, jaw & tooth structure
females preferentially mating with males that are more similar to themselves
separating as bottom vs top feeders

Question 10

example of behavioural sympatric speciation - killer whales (2 species names & differences)

Answer 10

resident vs biggs killer whales
resident killer whales maintain tight-knit family pods and prey on salmon and other marine fish.
bigg’s killer whales roam in smaller groups, preying on other marine mammals such as seals and whales

Question 11

example of temporal sympatric speciation - palm trees (2 species names & cause of speciation)

Answer 11

in australia (lord howe island)
howea forsteriana & howea belmoreana
speciation due to a substantial disjunction in flowering time

Question 12

example of temporal sympatric speciation - cicadas (2 species names & cause of speciation)

Answer 12

in eastern united states
m. tredicim & m. septendecim
m. tredecim emerge every 13 years, while adults of m. septendecim emerge every 17 years

Question 13

define species biodiversity

Answer 13

the number and relative abundance of species found in an area

Question 14

define ecological niche

Answer 14

the role of a species in an ecosystem

Question 15

4 characteristics of an ecological niche

Answer 15

the abiotic environmental conditions a species can tolerate (i.e. temperature, precipitation and terrain)

the biotic interactions a species has with other species (i.e. competition, predation and mutualism)

the activity pattern of the species (i.e. nocturnal, diurnal or crepuscular)

how the species obtains energy and nutrients from the environment (what and how it eats)

Question 16

define adaptive radiation

Answer 16

a pattern of speciation in which many species rapidly evolve from a common ancestor to occupy a range of vacant ecological niches (a source of considerable biodiversity)

Question 17

natural selection results in multiple related species exhibiting different ________, ________ and ________ adaptations to the new niches.

Answer 17

morphological, physiological, behavioral

Question 18

how may niches become available? x2

Answer 18

mass extinctions leave behind a host of empty niches. any remaining species can rapidly evolve to fill the niches without competition from the other (now-extinct) species.

because new species rarely make it to isolated islands, the few pioneering species that first arrive and colonize find a wide-open ecosystem with many niche vacancies and lack of competition with other species for available resources.

Question 19

how did dinosaur extinction impact adaptive radiation of mammals (before & after)? what did this lead to?

Answer 19

before the extinction, mammals were small and occupied few ecological niches
after the extinction, mammals evolved and adapted to the the newly available niches with few competitors for resources
this led to a “sudden” expansion of species diversity, including the first fully aquatic mammals, flying mammals, rodents and primates

Question 20

what were cynodonts (200+ million years ago)

Answer 20

a group of mammal-like reptiles

Question 21

3 characteristics of the early true mammals (~175 million years ago)

Answer 21

mainly small insect-eating creatures

adapted to nighttime activity

ranged in size from scarcely bigger than a bumblebee to squirrel-sized (keeping out of the way of the predatory dinosaurs)

Question 22

3 mamillian groups at ~140 million years ago

Answer 22

monotremes (platypus and spiny anteater), which lay eggs externally

marsupials (kangaroos, opossums), which carry their young in a pouch

placental mammals (humans, cows, horses), which retain the fetus internally during long gestation period

Question 23

what was the dinosaur extinction called? how many species of earth did it elimintate?

Answer 23

the cretaceous–paleogene

killed ~three-quarters of the plant & animal species

Question 24

watch this video on adaptive radiation https://www.youtube.com/watch?v=IPlOLaY5xbA

Answer 24

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Question 25

how did the galapagos finches experience adaptive radiation? & video to watch https://www.youtube.com/watch?v=mcM23M-CCog

Answer 25

one species of finch migrated to the galapagos from the mainland of central/south america this one migrant species would gives rise to multiple species that exploit different niches species have adapted for different diets: seeds, insects, flowers, the blood of seabirds, and leaves

Question 26

how have madagascar's ant nest beetles gone through adaptive radiation?

Answer 26

beetles imitate the sounds of an ant queen, permitting them access to the nest without alarming the other ants secretions on their antennae and body allow them to interact with ant workers without being detected

Question 27

how have hawaii's silversword plants gone through adaptive radiation?

Answer 27

have a range of anatomical and ecological adaptations but are very genetically similar are found in a range of terrestrial habitats (wet forests, dry forests, near sea level, in alpines, etc)

Question 28

how have the caribbean's anoles gone through adaptive radiation?

Answer 28

spread out across the islands once they arrived from south america anatomical differences in leg length and toe pad size, primarily related to moving on the substrate they most frequently encounter (eg. lizards that live on the ground have long legs for sprinting whereas twig dwelling lizards have short legs for grasping)

Question 29

define hybrid

Answer 29

the offspring resulting from the sexual reproduction between two closely related, but separate species

Question 30

why are hybrid plants often bred for?

Answer 30

increased yield and improved quality traits such as size, color, and flavor

Question 31

define prezygotic barriers

Answer 31

prevent fertilization of egg and sperm between two seperate species. these prevent any energy being wasted on the formation of a hybrid offspring.

Question 32

what do barriers to hybridization ensure?

Answer 32

energy is not spent producing sterile hybrids and preventing the mixing of alleles between species

Question 33

define postzygotic barriers

Answer 33

barriers that occur after fertilization that prevent the zygote from developing into a viable, fertile adult.

Question 34

examples of prezygotic barriers & definitions x5

Answer 34

habitat isolation (two species occupy different habitat and/or niche) temporal isolation (two species breed at different times of the day, season or year) behavioural isolation (two species have unique behaviours that attract only the like-kind species) mechanical isolation (differences in the anatomy of the reproductive organs may prevent successful breeding) gametic isolation (the proteins on the surface of the gametes will not be complementary, preventing successful fertilization)

Question 35

examples of postzygotic barriers & definitions x3

Answer 35

reduced hybrid viability (prevent the hybrid offspring from surviving) reduced hybrid fertility (prevent the hybrid from itself successfully reproducing) hybrid breakdown (see separate flashcard)

Question 36

define hybrid breakdown

Answer 36

if a first-generation (F1) hybrid is able to survive and reproduce with another hybrid or with either parent species, the offspring of the hybrid (F2) may be feeble or sterile due to incompatibility between interacting genes of the two species.

Question 37

define polyploidy. in what is it commonly seen?

Answer 37

there are more than two sets of chromosomes in each cell. most common in flowering plants (>70%)

Question 38

why are polyploidy usually bigger in size than diploid ones?

Answer 38

the nucleus has to expand to accommodate the extra genetic material

Question 39

how are polyploidy offspring different from their parents?

Answer 39

survive better than their parents in harsh environments, such as cold climates and high altitudes and latitudes

Question 40

define the condition of autopolyploidy

Answer 40

a polyploid individual will have two or more complete sets of chromosomes from its own species

Question 41

how may a diploid (2n) gamete be produced?

Answer 41

if there is an error in meiosis that results in all of the chromosomes moving into one cell instead of separating

Question 42

how are triploid (3n) and tetraploid (4n) zygotes created?

Answer 42

the diploid (2n) gamete can then fuse with a haploid gamete from the same species to create a triploid (3n) zygote, or with another diploid gamete of the same species to create a tetraploid (4n) zygote

Question 43

define allopolyploid

Answer 43

a polyploid with multiple chromosome sets derived from two different species

Question 44

how are allopolyploids created?

Answer 44

gametes from two species, at least one of which has had an error in meiosis, combine to form allopolyploid offspring

Question 45

why are polyploids immediately reproductively isolated?

Answer 45

as chromosome number is a shared trait within a species, polyploid offspring have a different number of chromosomes than the parent species, and as a result the offspring is unable to breed with members of the parent species

Question 46

speciation due to polyploidy is a mechanism of what?

Answer 46

sympatric speciation

Question 47

examples of polyploidy species x2

Answer 47

allium (onion, garlic, chives, scallion, shallot and leek) coast redwood (hexaploid) (long lived tall trees)

Question 48

lamarckism 2 main ideas (state & explain) & an example

Answer 48

use and disuse: structures that are used frequently and continuously will strengthen, develop, and enlarge, while structures that are not used will weaken and deteriorate. inheritance of acquired characteristics: the physical changes to the structures of an organism that result from use/disuse during their lifetime are inherited by its offspring ancestral giraffes stretching necks caused offspring to inherit stretched necks

Question 49

charles darwin proposed a mechanism of evolution called what?

Answer 49

natural selection

Question 50

how is lamarckism's proposal of inheritance replaced by darwin through a paradigm shift?

Answer 50

because we now understand that physical changes that occur during an organism's lifetime are not passed to offspring

Question 51

define homologous structures

Answer 51

structures derived from the same body part of a common ancestor. they may not always have the same function

Question 52

define analogous structures

Answer 52

structures that have different evolutionary origins, but perform the same function. does not imply a recent common ancestor

Question 53

speciation is often depicted using what type of diagram?

Answer 53

a branching line diagram

Question 54

why can it be hard to distinguish genetically diverging populations as the speciation process is occurring?

Answer 54

because there is a continuum from merely somewhat restricted gene flow within the ancestral species and the complete reproductive isolation of the 2 resulting species

Question 55

define reproductive isolation as the first step in speciation. how can it be seen?

Answer 55

populations stop interbreeding with each other (for speciation to occur there must be barriers that prevent gene flow between the gene pools of two populations) can be geographic, behavioural or temporal

Question 56

define gene flow

Answer 56

the movement of genes into or out of a population

Question 57

define how differential selection acts as the second step in speciation

Answer 57

if the divergence in traits results in the populations not being able to interbreed should they once again overlap then the populations are now different species according to the biological species concept

Question 58

videos on slides 18, 19 and 23

Answer 58

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