Question

someone help please

Week 8 Discussion Question Title: Reproductive Barriers Explain how Pre-Post Zygotic Barriers impede mating and / or development of an organism. Provide an example of each category.

Answer 1

PREZYGOTIC BARRIERS -ANYHTHING THAT PREVENT MATING AND FERTILIZATION IS A PREZYGOTIC BARRIER.

PREZYGOTIC BARRIERS ARE: HABITAT ISOLATION ,TEMPORAL ISOLATION,BEHAVIORAL ISOLATION,MECHANICAL ISOLATION AND GAMETIC ISOLATION.

HABITAT ISOLATION :OCCURS WHEN TWO SPECIES OCCUPY DIFFERENT HABITATS.

EG. TWO SNAKES OF THE SAME GENUS LIVE IN THE SAME AREA BUT ONE IS AQUATIC AND OTHER IS TERRESTRIAL.

TEMPORAL ISOLATION: OCCURS WHEN TWO SPECIES MATE AT DIFFERENT TIMES OF A YEAR.

EG: FROGS LIVE IN THE SAME POND BUT BREED DURING DIFFERENT TIMES OF A YEAR ( SUMMER AND SPRING)

BEHAVIORAL ISOLATION : OCCURS WHEN TWO SPECIES HAVE DIFFERENT COURTSHIP BARRIERS.

EG: CERTAIN GROUP OF BIRDS RESPOND ONLY TO SPECIES SPECIFIC MATING CALLS.

MECHANICAL ISOLATION: OCCURS WHEN PHYSICAL  DIFFERENCES PREVENT COPULATION OR POLLINATION.

EG: CERTAIN GROUP OF DOGS ARE MORPHOLOGICALLY INCAPABLE OF MATING BECAUSE OF DIFFERENCE IN SIZES.

GAMETIC ISOLATION : GAMETES OF ONE SPECIES FUNCTION POORLY WITH THE GAMETES OF ANOTHER SPECIES.

POST ZYGOTIC BARRIERS:POST ZYGOTIC BARRIERS PREVENT A HYBRID ZYGOTE FROM DEVELOPING INTO A VIABLE , FERTILE ADULT.

POST ZYGOTIC BARRIERS ARE HYBRID INVIABILITY , HYBRID INFERTILITY, HYBRID BREAK DOWN.

HYBRID INVIABILITY : HYBRIDS ARE PRODUCED BUT FAIL TO DEVELOP

EG  :CERTAIN TYPES OF FROGS FROM HYBRID TADPOLES DIE BEFORE THEY CAN BECOME A FROG.

HYBRID INFERTILITY: HYBRIDS FAIL TO PRODUCE FUNCTIONAL GAMETES.

EG: MULES ARE STERILE HYBRIDS RESULTING FROM MATING BETWEEN A HORSE AND A DONKEY.

HYBRID BREAK DOWN: F1 HYBRIDS ARE FERTILE BUT F2 GENERATION FAIL TO DEVELOP PROPERLY.

EG: THE OFFSPRING OF HYBRID COPEPODS HAVE LESS POTENTIAL FOR SURVIVAL OR REPRODUCTION