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 fertilization and explain the difference between oviparous, viviparous, and ovoviviparous animals, providing an example of each.

Explain what a gamete is and two differences from a somatic cell (chromosome complement, function), discussing why gametes cannot have the same complement as the rest of the cells.

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).

What is courtship? Give two examples (the peacock's tail, birdsong, the bellowing of the deer) and explain its functions (recognizing the species, selecting a mate, synchronizing reproduction).

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

Distinguish between direct and indirect development with an example of each (a mammal and a butterfly or an amphibian), and indicate what the existence of a larval phase implies in the life of the animal.

Compare the reproductive strategy of an amphibian and a reptile: type of fertilization, egg structure, and site of development, highlighting what innovation the amniotic egg represented for the colonization 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-fertilize with another individual rather than self-fertilize.

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 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 specialized bodies, cannot reproduce this way.

The reproductive cycle of amphibians remains tied to water: gelatinous spawn, external fertilization 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.

What is sexual dimorphism? Give two examples (the antlers of the deer, the colors of birds, the lion's mane) and relate it to sexual selection: competition between males and mate choice by females.

Many corals release their gametes on the same night of the year, synchronized with the moon and the tides. Explain what advantage this mass synchronization has in animals with external fertilization and which environmental signals can guide it (photoperiod, temperature, the lunar cycle).

The rutting season of many mammals occurs on very regular dates. Explain how the photoperiod (day length) regulates the breeding season and discuss what advantage scheduling births for spring has (food, temperature, time to grow before winter).

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 paleontology team discovers the fossils of a new primitive Carboniferous tetrapod. Its skeleton lacks copulatory structures, and masses of thousands of tiny fossilized unmineralized 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 fertilization 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.