Exercises: 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.

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

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.

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.

Describe the metamorphosis of a frog from egg to adult, indicating the most important anatomical and physiological changes and their relationship to the transition from an aquatic to a terrestrial environment.

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.

On an oceanic island newly emerged after a volcanic eruption, two species of herbivorous insects are accidentally introduced: a solitary female of species A (which reproduces by obligate parthenogenesis) and a pair (male and female) of species B (obligate amphimictic sexual reproduction). a) Predict the demographic dynamics and the rate of colonization of both populations during the first 10 generations in an environment without competition or predators. b) In generation 15, a lethal pathogenic fungus colonizes the island. Justify which population will be more likely to go completely extinct and which will be able to present resistant individuals. c) Based on the above, reason the paradox of the "twofold cost of sex": if parthenogenesis allows a population to grow twice as fast by not producing males, why is sexual reproduction predominant in multicellular animals?

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.