Lecture 21 Flashcards
Reproduction
How do physiological mechanisms influence animal reproduction?
Physiological mechanisms govern the functioning of reproductive systems in animals, including the production and release of gametes (sperm and eggs), hormonal regulation, and the alignment of reproductive activity with environmental cycles like temperature or photoperiod. These processes ensure successful reproduction within a species.
Why is animal reproduction considered incredibly diverse?
Animal reproduction is highly diverse due to the variation in reproductive systems and strategies across species. For instance, some animals reproduce sexually, others asexually (like parthenogenesis), and there are significant differences in reproductive anatomy, timing, and coordination with environmental cues, such as seasonal changes.
What are induced and spontaneous ovulators?
Induced ovulators are animals whose ovulation (the release of mature eggs) occurs in response to copulation, such as in rabbits or shrews. Spontaneous ovulators, like humans, dogs, and cows, undergo ovulation independently of mating, based on internal hormonal cycles.
How does the environment influence animal reproduction?
The environment plays a key role in timing reproduction. Seasonal changes in photoperiod (the length of day and night) are particularly important as they signal the optimal time for mating and reproduction in many species. For example, rabbits in northern climates exhibit seasonal cycles of reproductive competency based on photoperiod changes.
What is the difference between semelparous and iteroparous species?
Semelparous species reproduce only once during their lifetime, often at the end of their lives, and then die (e.g., salmon, mayflies). Iteroparous species, on the other hand, reproduce multiple times throughout their lives, typically with reproductive cycles that occur annually or periodically (e.g., most mammals).
What is the role of parental investment in reproductive strategies?
Parental investment refers to the resources and care provided by parents to ensure the survival and development of offspring. It can include provisions like egg yolk, placental nutrients, lactation, or post-hatching feeding. This investment is crucial in determining reproductive strategies and whether a species is more likely to engage in semelparity or iteroparity.
How do animals coordinate reproductive cycles with environmental cues?
Some animals tightly coordinate reproductive cycles with environmental factors, ensuring that reproduction occurs at the best time for offspring survival. This may involve synchronized hormonal changes, the timing of ovulation, and responses to cues such as temperature, light cycles, or food availability. However, many species have evolved mechanisms to decouple certain reproductive steps, such as sperm storage or delayed diapause in response to environmental conditions.
What is diapause, and how does it relate to environmental timing in reproduction?
Diapause is a period of suspended development in some animals’ embryos, often triggered by environmental cues such as temperature or food availability. For example, in certain species, a peptide neurohormone is produced by the mother, initiating diapause in the eggs. The process can be paused until favourable environmental conditions, like a cold period, signal the embryo to continue developing.
