Transcript of Reproduction
How much should be invested in each offspring?
Why so many sperm?
• Why do males produce thousands of sperm rather than one sperm for one egg?
• Listen to the following audio recording to learn more.
• Apply this information to complete the worksheet.
How much to invest in an egg?
• Animals have a certain amount of resources for reproduction
• They can lay many small eggs, of which only a few will be fertilised and then survive – Invest little per egg
• They can lay larger eggs (with more yolk) or give birth to live young, producing less eggs, but each one having a larger chance of being fertilised and surviving.– Invest a lot per egg
What environmental conditions lead to a smaller/ larger investment?
• Read notes from page 374-376– Why broadcast spawn at sea?– Why broadcast spawn during flood events?– What sort of conditions would be best for laying
demersal eggs?– What sort of increased investment is seen in
species that lay demersal eggs?
R or K- selection?
• Read your notes from 381-382– Animals that have one breeding season are likely
to be ____________________– Define fecundity– A risk of r-selection is self fertilisation. How can
this be avoided?
Linking r/K-selection to understanding oviparous and viviparous animals
• Read notes from 383-387– Why do animals that lay eggs in a terrestrial
environment have to invest more in each egg?– What would be the difference between the eggs
of r-selected species and K-selected species?– What is the difference between egg-yolk viviparity
and placental viviparity?• Would these strategies show r or K-selection?
• We have a SAC next Monday• This will cover all of chapter 11 and 12• You will be expected to be able to – Identify types of behaviour (both innate and learned)– Mating systems– Plant behaviour (data analysis)– Discuss reproductive investment (r of K selected)– You will be given scenarios or data and be asked to predict
behaviour or reproductive strategies.– Marks will be awarded on your ability to use the language
and argue your theory