fighting Flashcards
cases of serious fighting involve:
- Males fighting for access to females/ breeding sites
- Females fighting for access to males
- Animals disputing over food
Fighting for territory - Groups fight for territory in a few species
Serious fights between animals are generally between ____ competing for breeding access to ______.
males
females
Fighting results ultimately from males ________, and this in turn results from sexual rather than asexual reproduction.
being different from females
does it pay to produce as many sons as daughters
yes
what have females become specialized in?
parental care
1 way males can pass on their genes
competing for breeding access to females
fitness equation causing sexual reproduction
F=1/2nSj + Sa
F = fitness n = number of offspring Sj = proportion of juveniles surviving from birth to 1st breeding Sa = proportion of adults surviving from one breeding attempt to the next
Which would do better?
A gene which makes its carriers risk little to get 10 offspring
n = 10; Sj = 0.1; Sa = 0.6
Or a gene which makes its carriers risk a lot to get 20 offspring
n = 20; Sj = 0.1; Sa = 0.3
2nd one
- 1
- 3
how can males increase their fitness?
- Paternal care (small minority of species)
- Produce ornaments that appeal to females (e.g., widow birds)
- Fight for breeding access to females (or breeding sites)
why do red deer walk in parallel?
assessment of the opponent’s size
reduce chance of needless injury
fitness definition
a measure of how fast the gene spreads in the population
x= generation
y= gene frequency
graph
SEE POST IT
fitness equation causing asexual reproduction
F=nSj + Sa
F = fitness n = number of offspring Sj = proportion of juveniles surviving from birth to 1st breeding Sa = proportion of adults surviving from one breeding attempt to the next
gene causing its carriers to reproduce asexually spreads …
nearly twice as fast as a gene causing its carriers to reproduce sexually
= x2 cost of sex
why are males and females different?
· Evolutionary biologists define males and females in terms of the types of gamete they produce
Specialised gametes do better than general purpose gametes
evolutionary biologists define males and females in terms of what?
types of gametes they produce
Cell packed with nutrients to allow embryo growth
eggs
Cell adapted to swim to find another gamete to combine with
sperm
Specialised gametes do ____ than general purpose gametes
better
Why are there so many males?
- Not many needed to fertilize the available females
- if deviation from 1:1 then mothers producing rarer sex favoured
what would happen if there was a deviation from mothers producing 50:50 sons to daughters
mothers producing the rarer sex would be favoured by natural selection. This returns the population to a 50:50 sex ratio.
what is a lek?
aggregation of male animals gathered to engage in competitive displays, lekking, to entice visiting females which are surveying prospective partners for copulation
e.g. ruffs, damselflies, uganda kob, black grouse, sage grouse, white- bearded manakin
why 1:1 ratio of males to females
- a gene spreads causing females to produce FEWER sons than daughters
- Then on average males would have more offspring than females
- Then females producing mostly sons would get more grandchildren than females producing mostly daughters
- So a gene causing females to produce mostly sons would spread
