L4-Sex,allee effects,plasticity, fertilisation Flashcards
What are the Basic population dynamics?
• Population next year = Population x Births – Deaths
• Births straightforward on land
• Competition tends to reduce resources and so
as population increases, birth rate decreases
What happens as pop increases in land animals?
birth rate decreases
What are the two types of Internal fertilisation?
- Copulatory
- Non-copulatory-some sponges filter out sperm
What fertilisation do most groups use?
External fertilisation
What is Ancestral mode of reproduction?
External fertilisation
How common is external fertilisation?
50% of all species
What happens with distance in external fertilisers?why?
Sperm dilution
fertilisation success drops
How do you get high fertilisation success?
High density = High fertilisation success,
lots of genetic mixing
How does the relationship between distance and success change with distance for both types of fertilisation?
internal fertilisers constant
external bell curve
What are Alle effects?
At very low population densities, population
growth rates decreases due to mate limitation
What are most affected by allee effects?
External fertilisation
how does Allee effects and recovery from
disturbance?
if individuals die eg. bleaching dispersal distances are increased
What is protandry?
changing from females to males
Why protandry?
large males get most mating success
How can protandry leave a species vulnerable?
on sex may be hunted more
