Chapter 22

temporal isolation

form of reproductive isolation in which two populations reproduce at different times

prevention of gamete fusion definition

gametes of one species function poorly with the gametes of another species or within the reproductive tract of another species

Speciation is more likely in geographically isolated populations because what does not occur?

gene flow

What process can promote speciation through random changes between isolated populations?

genetic drift

Hybrid inviability or infertility

hybrid embryos do not develop properly, hybrid adults do not survive in nature, or hybrid adults are sterile or have reduced fertility

What isolating mechanism is postzygotic?

hybrid sterility

Reinforcement

initially incomplete isolating mechanisms are reinforced by natural selection until they are completely effective it is not inevitable- hybrids may be inferior but may still be fertile serve as conduct genetic exchange

When species are kept separate by preventing the formation of hybrid zygotes, the mechanism that keeps the species separate is known as a _____________ isolating mechanism.

pre zygotic

In the southeastern U.S., two species of wild lettuce (Lactuca) do not usually form hybrids, because they bloom at different seasons. The means of isolation appears to be

prezygotic and temporal.

Members of different species cannot interbreed successfully due to ___________ _________ ___________

reproductively isolating mechanisms

the biological species concept

species composed of populations whose members mate with each other and produce fertile offspring

ecological isolation

species occur in the same area, but they occupy different habitats and rarely encounter each other

Gene exchange

the biological species concept focuses on the ability to change gene

Polyploidy

the state of a cell or organism having more than two paired sets of chromosomes.

ecological isolation

tiglon do not occur in the wild lions and tigers ranges overlap in india but they use different habitats they not not encounter each other

Sympatric speciation occurs _______ geographic separation.

without

Hybrid inviability or infertility example

A mule

behavioral isolation example

Blue footed boobies mate only after a courtship display unique to their species

behavioral isolation

Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding

temporal isolation

-2 species of wild lettuce grow going roadsides in SE US -hybrids made experimentally and fertile -rare in mature since 1 flowers in the spring and 1 in the summer

what contributed to the adaptive radiation of Darwin's finches on the Galápagos Islands?

-Lack of mainland bird types -Geographic isolation -Vacant ecological niches

Behavioural isolation

-blue footed boobies select mates after countship -sympatric species avoid mating with members of wrong species in variety of ways including... visual signs, electrical signals, sound production, chemical signals: pheromones

prevention of gamete fusion with example

-gametes of one species function poorly with the gametes of another species or within the reproductive tract of another species. example: sperm and eggs cannot form (monkeys and humans)

postzygotic isolating mechanisms

-hybrids that do not survive may be weaker -hybrids may be sterile -mules -could have abnormal sex organs or failure to form gametes -chromosomes cannot be pair properly in meiosis

Criticisms of biological species concept

-reproductive isolation may not be the only force maintaining species integrity -interspecific hybridisation -difficult to apply concept to populations that are geographically separated in nature -many species that don't hybridise in the wild will do so in captivity -asexual -possible that different processes maintain species

geographic variation

-within a single species, individuals in populations that occur in different area may be distinct -even though geographically distant populations may appear distinct, they usually connected by intervening population that are intermediate in their characteristics

In contrast, the_______ species concept suggests that separation of species is maintained by natural selection in which each distinct species has _________ to its own specific part of the environment.

1. ecological 2. adapted

two concepts of the nature of species

1. the distinctiveness of species that occur together at a single locality 2. the connection that exists among different populations belonging to same species

The evolution of these organisms is an example of adaptive radiation because populations were isolated and adapted to newly formed islands or habitat patches formed by lava flows.

Hawaiian Drosophila

what is best cause and effect sequence for the process of speciation by natural selection?

Mutation --> Variation --> Selection --> Reproductive Isolation --> Speciation

According to the __________ species concept, a species is comprised of populations in which members mate with each other and produce fertile offspring.

biological

The idea that species are defined based on the ability to interbreed with each other and exchange genes

biological species concept

Sympatric speciation also can occur over multiple generations, particularly if _________ selection favors two different phenotypes.

disruptive

reproductive isolation

do not mate with each other or don't produce fertile offspring

ecological species concept

each species adapted to its environment... 1. distinctions among species are maintained by natural selection 2. stabilising selection maintains the species adaptions 3. hybrids are quickly eliminated from gene pool 4. strong selection overwhelms gene flow

________ isolation is another term for environmental

ecological

Two bird species have different mating calls, occupy different habitats in nature, and when they hybridize, the hybrids are infertile. What isolating mechanisms maintain these species?

ecological isolation, behavioral isolation, and hybrid sterility

temporal isolation example

Orchids that bloom on different day can only pollinate their flowers only when they bloom at the same time.

Prezygotic

Reproductive barrier that prevents a species from mating includes ecological, behaviour, temporal, mechanical isolation, and prevention of gamete fusion

adaptive radiation

The phenomenon where one species diverges into many by occupying a different habitats within a region

character displacement

The process by which related species become more different in order to reduce competition

Mechanical isolation example

many insects cannot mate because their sex organs do not fit together, which prevents the transfer of sperm

mechanical isolation

mating is attempted, but morphological differences prevent its successful completion

Males of many marsupial species have forked penises that are incompatible with the anatomy of female placental mammals. What type of isolating mechanism does this represent?

mechanical incompatibility

reproductive isolating mechanisms

mechanisms that prevent interbreeding between different species

Postzygotic

mechanisms that prevent proper functioning of zygotes after they form includes hybrid inviability or infertility

One type of sympatric speciation that is common in plants is polyploidy, where parents produce offspring with ______ ______ ______ sets of chromosomes that are reproductively isolated from other members of its species.

more than two

Many species might coexist in a particular environment by occupying different ecological

niches

what is an example of temporal isolation?

one plant species blooms in June-July and a second plant species blooms in August-September.