Chapter 18 pt 2 ppt flashcards

Question 1

stopping gene flow promotes

Answer 1

isolation

Question 2

reproductive isolating mechanisms

Answer 2

• prevent individuals of different species from mating and producing viable offspring
• by reducing the chances of INTERSPECIFIC mating and production of hybrid offspring-these isolating mechanisms,s prevent the gene pools of distinct species from mixing
• isolating mechanisms operate at different times

Question 3

interspecific

Answer 3

btwn species

Question 4

prezygotic isolating mechanisms

Answer 4

• before fertilization and production of zygote
• prevent the production of hybrid offspring

Question 5

postzygotic isolating mechanisms

Answer 5

• after fertilization and zygote formation
• reduce the success of hybrid individuals

Question 6

these mechanisms are not …..

Answer 6

mutually exclusive
- two or. more of them may affect the outcome of between species interaction

Question 7

prezygotic isolations

= premating

Answer 7

ecological isolation=species live in different habitats

temporal isolation=species breed at different times

behavioural isolation=species can’t communicate

mechanical isolation=species can’t physically mate

gametic isolation=species have non matching receptors on gametes

= 5 mechanisms that can prevent the production of hybrid offspring

Question 8

postzygotic mechanisms

= postmating

Answer 8

hybrid inviability- hybrid offspring do not complete development

hybrid sterility- hybrid offspring cannot produce gametes

hybrid breakdown- hybrid offspring have reduced survival or fertility

Question 9

N=4; prezygotic

Answer 9

N=4
- mechanisms limit the frequency of interspecific matings

Question 10

N=1;prezygotic

Answer 10

N=1
- blocks interspecific fertilizations
- gametic isolating mechanism

Question 11

ECOLOGICAL ISOLATION

Answer 11

• occurs when species in the same geographic region live in different habitats
  = might live in the same country but different habitats
• example: lions live in open grasslands typically, versus tigers that live in dense forests
• 2 species don’t encounter one another and do no interbreed in wild
• in captivity, lion-tiger hybrids occur sometimes

Question 12

LIGER

Answer 12

ecological isolation

• Liger (lion-tiger hybrid)
• male lion and female tiger
  = this disruption doesn’t turn off or lower the growth gene because usually the mom will block it to prevent the baby from growing too big/fast but here the mom is the TIGER
• 750-1000 lbs
• lion dad passes on growth-promoting gene but antagonistic gene from female is absent
• not seen in nature

Question 13

TEMPORAL ISOLATION

Answer 13

• species living in the same habitat can experience temporal isolation–if they mate at different times of the day or different times of the year

-will never hybridize or breed because they leave seeds at different times

• e.g. : pinus radiata and pinus muricarta
• p. radiata releases pollen February whereas P. murticat release spleen in April

Question 14

overlap in geographic distribution

Answer 14

• but don’t interbreed

Question 15

BEHVAIOURAL ISOALTION

Answer 15

• many animals rely-on specific-specific signals
• many recognized by other species to identify mates
• behavioural isolation happens whrene signals uses by one species are not egagered

e.g. feel birds rely on song, colour, and disables to recognize eachother,

e.g. similar to foreign language another species doede understand

Question 16

hooded warblers

Answer 16

In hooded warblers, behavioral isolation occurs when individuals from different species or populations do not recognize or respond to each other’s courtship songs and displays, preventing interbreeding. This ensures mating only occurs within the same species.

Question 17

firefly flashing pattern xample

Answer 17

• bioluminescent\ent signals
• used to attract males
• diff flashing patterns in 9 species
• females Only respond to display given the males of their species

Question 18

Behavioural Choice-mate choice

Answer 18

-mate choice by females and sexual selection drive evolution of mate recognition signals

• females invest a lot of energy into reproduction
• strong selection against choosing wrong species
• genes for wrong choice of species would be weeded out of population quickly (would not pass on their genes, assuming hybrids not fertile)

Question 19

Mechanical Isolation

Answer 19

• differences in structure of reproductive organs (or other body parts) may prevent individuals of different species from interbreeding
• e.g. plants have morphological traits that only allow certain pollinators (bird/insect) to collect and distribute pollen
• case study: purple monkey flower (Limulus Lewisii) and scarlet monkey flower (Mimulus Cardinalis)
• Overlap in distribution in state of California

Question 20

Purple monkey flower vs Scarlet monkey flower

Answer 20

Purple Monkey Flower
- pollinated by bumblebees
- landing petals for bees
- yellow stripes=nectar guides
- drink nectar and pick up pollen

Scarlet Monkey Flower
- pollinated by hummingbirds
- reproductive parts extend beyond petals
- red attracts hummingbirds (but outside of range for bees)

Question 21

GAMETIC ISOLATION

Answer 21

• even when different species do mate–incompatibility of the sperm of one species and the eggs of another which may prevent fertilization
• e.g. broadcast spawning marine invertebrates
• release gametes into the open ocean for external fertilization
• sperm and eggs of different species recognize each other via their respective surface proteins (e.g. JUNO is the egg cell that recognizes its sperm counterparts (IZUMOI) in mammals)

this allows for the egg to establish recognition for correct sperm ONLY

Question 22

Postzygotic Isolating Mechanisms

Answer 22

• if pre-zygotic mechanisms are ineffective, sperm from one species sometimes fertilizes an egg from another species
• 2 species will be reproductively isolated if their offspring (interspecific hybrids) have lower fitness than offspring from intraspecific matings
• 2 post-zygotic isolating mechanisms exist

fully-formed fetus in embryo

Question 23

Postzygotic Isolating Mechanisms

Answer 23

1) hybrid invariability: species hybrids not surviving

2) hybrid sterility: species hybrids not producing functional gametes

3) hybrid breakdown: reduced fitness of F2
= usually due to inbreeding depression

Question 24

Hybrid Inviability

Answer 24

• hybrids have 2 sets of developmental instructions
• one from each parent species– which may not interact properly in relation to embryonic development
• hybrids often die as embryos because of incompatible developmental pathways at an early age (known as hybrid inviability)
• e.g. sheep and goats can mate and fertilize one another’s ova BUT the embryo always die before coming to term (incompatible developmental pathways)

Question 25

Hybrid Sterility

Answer 25

- some hybrids may develop into healthy adults but may not produce functional gametes (HYBRID STERILTIY) - due to parent species having a different number of chromosomes which cannot pair properly during meiosis - these hybrids have 0 fitness because they leave no offspring (also called evolutionarily dead because they cant produce more offspring) - e.g. mule=female horse (2n=64) and male donkey (2n=62)

Question 26

hybrid breakdown

Answer 26

- some f1 (first-generation) hybrids are healthy and fully fertile - can breed with other hybrids and with both parental species - BUT F2s produced via matings between F1 hybrids (or F1 and either parental species) may exhibit reduced survival or fertility (=hybrid breakdown) HYBRID BREAKDOWN: - genetic stand - functionally non-existent - hard to survive and find a mate is impaired

Question 27

the geography of speciation

Answer 27

- Ernest Mayr recognized that geography hade a huge impact on whether gene pools had the chance to mix 2 MODES OF SPECIATION: - allopatric (physically separated): evolution of reproductive isolating mechanisms between 2 populations that are geographically separated - sympatric: speciation that occurs without the geographical isolation of populations (live on the same area, but are separated with a barrier) (main drivers: sexual selection, w/ enough sexual selection 2 species can co-exist but remain separate)

Question 28

allopatric speciation

Answer 28

takes place when a physical barrier subdivides a large population or when a small population becomes separated from a species' main geographical distribution (2 main steps) - STEP 1: populations become geographically separated, preventing gene flow between them - STEP 2: as popns experience mutations and different patterns of NS and genetic drift, they may accumulate genetic differences that isolate them reproductively = unique and different environments produce different forms of natural selections which produces genetic differences

Question 29

4 steps of allopatric speciation

Answer 29

1) at first a population is distributed over a large geographical area 2) a geographical change separates the original population (i.e. tectonic plates), creating a barrier to gene flow 3) in the absence of gene flow, the separated populations evolve independently and diverge into different species over time 4) when another geographical change allows individuals of the two species to come into secondary contact, they do not interbreed (test to see if they're reproductively isolated and separate species)

Question 30

if during secondary contact, species breed and produce babies, then this is representative of what phenomenon

Answer 30

species fusion

Question 31

geographical separation case study

Answer 31

2 SPECIES: CORTEZ RAINBOW WRASSE AND BLUE-HEADED WRASSE - genetically different with a common ancestor ------------------------------------------------------ - 5 MYA uplift of the Isthmus of Panama - seperated once continuous shallow sea into eastern tropical Pacific Ocean and western tropical Atlantic Ocean = became a separation for marine animals between atlantic and pacific oceans - mutation, NS, and drift differed on each side - populations diverged genetically and pairs of closely related species lie on either side now

Question 32

Archipelago Spices Cluster

Answer 32

1) a few individuals of a species from the mainland arrive on isolated islands A and B 2) over time, they differentiate into new species on these islands. the purple species then colonizes islands C and D 3) over time, the populations on islands C and D differentiate into 2 new species - develop unique adaptations to their environment...NS 4) some time later, the blue species colonizes island A, and the orange species colonizes island B, establishing secondary contact

Question 33

why do we use islands

Answer 33

- seperated so its easier to measure features - easy to date: carbon dating

Question 34

secondary contact- test of allopatric speciation

Answer 34

- allopatric populations can reestablish contact when barrier is eliminated or breached (step 4 last slide) SECONDARY CONTACT: contact after a period of geographical isolation provides a test of whether the genes in a population have diverged enough to make them reproductively isolated = this is the only test to determine if they've changed - if not very different, species will interbreed and merge into one= species fusion

Question 35

hybrid zones

Answer 35

hybrid zones: geographic area where the hybrid offspring of two divergent species are common

Question 36

reinforcement

Answer 36

- evolution of prezygotic barriers to reproduction after post zygotic barriers exist

Question 37

Sympatric Speciation

Answer 37

within a population - reproductive isolation evolves between subgroups that arise within a population - does not require population be separated geographically - HOST RACE: arises from mutations favouring genetically distinct host of parasite (apple maggot case study)

Question 38

HOST RACE

Answer 38

arises from mutations favouring genetically distinct host of parasite (apple maggot case study) - species on an insect sticks to 1 host i.e. apple maggot to apple tree

Question 39

POLYPLOIDY

Answer 39

species have multiple sets of chromosomes (plants), can't breed with parent species

Question 40

sympatric speciation case study

Answer 40

apple maggot case study: - host plant in eastern NA is hawthorn - 2 host species have appeared in last 150 years - reside on apples and cherries - controlled by just a few genes [therefore, passed on easily and keep offspring separate]

Question 41

genetic mechanisms of speciation

Answer 41

- genetic divergence in allopatric populations can lead to speciation - polyploidy is a common mechanism of sympatric speciation in plants - chromosome alterations can foster speciation