Types and structures of reproduction

Differentiate between asexual and sexual reproduction in terms of the number of parents, genetic variability of the offspring, and reproduction rate, indicating an advantage of each type.

Name two types of asexual reproduction (for example, binary fission, budding, or fragmentation), an organism that uses them, and the distinguishing feature of each.

A starfish can regenerate an arm, and a planarian cut in two gives two individuals. Explain what relationship there is between this capacity for regeneration and asexual reproduction by fragmentation, and discuss why vertebrates, with such specialised bodies, cannot reproduce this way.

Define internal and external fertilisation and explain the difference between oviparous, viviparous, and ovoviviparous animals, providing an example of each.

Distinguish between oviparity and viviparity with two examples of each, and point out one advantage and one disadvantage of each strategy (protection of the embryo versus the parent's energy investment).

Compare the reproductive strategy of an amphibian and a reptile: type of fertilisation, egg structure, and site of development, highlighting what innovation the amniotic egg represented for the colonisation of land.

Explain what parental care is and describe three different forms (incubation of eggs, feeding of the young, defence of the territory or carrying of the young) with an animal example of each.

Earthworms and snails are hermaphrodites. Explain what this means, what advantages it offers to animals with low mobility, and why, despite this, they usually cross-fertilise with another individual rather than self-fertilise.

A naturalist claims: "To restore the fauna of a degraded wetland subject to unpredictable droughts, it is preferable to introduce K-selected species rather than r-selected species, since, by caring for their offspring, they ensure an extremely high survival rate and will reach a viable population sooner." a) Reasonably refute the naturalist's claim using the concepts of biotic potential, carrying capacity ($K$), and survivorship curves. b) Predict how the population size of an r-selected species versus a K-selected species will evolve if, two years after their introduction, an unexpected catastrophic drought occurs.

The reproductive cycle of amphibians remains tied to water: gelatinous spawn, external fertilisation and aquatic larvae. Explain this dependence and why many species return to the same pond every year (philopatry), as well as the risk posed by the disappearance of water points.

A palaeontology team discovers the fossils of a new primitive Carboniferous tetrapod. Its skeleton lacks copulatory structures, and masses of thousands of tiny fossilised unmineralised shell-less eggs have been found alongside the fossils in sediments from a river floodplain. A researcher on the team claims that this animal already exhibited fully terrestrial reproduction independent of water. a) Refute the researcher's hypothesis by pointing out the physical and cellular impediments (gametic desiccation, sperm motility, and zygote osmoregulation) that make external fertilisation unviable on dry land. b) Justify which anatomical and physiological evolutionary innovations in the gametes and the egg were necessary for amniotes to become independent of the aquatic environment for reproduction. c) Predict what differences you would expect to find in the yolk volume of the ova and in the number of gametes produced per cycle between this fossil and a terrestrial reptile of similar size.

Only two living females of the northern white rhinoceros (Ceratotherium simum cottoni) survive in the world, both unable to carry a pregnancy to term. However, cryopreserved semen from several deceased males and related females of the southern white rhinoceros subspecies are available in zoos and reserves. a) Design a sequential biotechnological protocol (from obtaining biological material to the birth of a calf) to rescue the subspecies using assisted reproduction techniques such as transvaginal ovum pick-up, intracytoplasmic sperm injection (ICSI), and embryo transfer to surrogate mothers. b) Justify why conventional artificial insemination is not applicable in this situation and what biological relevance the cryopreservation of the gamete bank has for the conservation of the species' allelic diversity. c) If three live calves originating from a single male and a single female are achieved through this strategy, critically assess the biological viability of reintroducing this new lineage into the wild without crossbreeding it with the southern white rhinoceros.