Unit 2 KA4 Flashcards
Female Investment
Egg structure in non-mammals or in uterus and during gestation in mammals
Parental Investment Pros and Cons
Increases probability of production and survival of young
Costly
Classification of r-strategists and K-strategists
Based on level of parental investment in offspring and number of offspring produced
Characteristics of r-selected species
Smaller
Limited parental care
Shorter generation time
Mature more rapidly
Reproduce earlier in lifetime although often only once
Produce larger number of smaller offspring
Each only receives a smaller energy input
Most offspring will not reach adulthood
Characteristics of K-selected species
Larger and live longer
High level of parental care
Mature more slowly
Can reproduce many times in their lifetime but relatively few
Larger offspring
High level of parental care
Many offspring have a high probability of surviving to adulthood
Where does r-selection occur
Unstable environments where the species has not reached its reproductive capacity
Where does K-selection occur
Stable environments
Benefit of External Fertilisation
Very large numbers of offspring can be produced
Cost of External Fertilisation
Many gametes predated or not fertilised
No or limited parental care
Few offspring survive
Benefits of Internal Fertilisation
Increased chance of successful fertilisation
Fewer eggs needed
Offspring can be retained internally for protection and/or development
Higher offspring survival rate
Costs of Internal Fertilisation
Mate must be located which requires energy expenditure
Régurgites direct transfer of gametes from one partner to another
What are mating systems based on?
How many mates an individual has during one breeding season
Monogamy
Mating of a pair of animals to the exclusion of all others
Polygamy
Individuals of one sex have more than one mate
Polygyny
One make mates exclusively with a group of females
Polyandry
One female mates with a number of males in the same breeding season
Successful Courtship in Birds and Fish
As a result of species-species sign stimuli and fixed action pattern responses
Benefit of sexual selection
Increases individuals chances of mating
Product of sexual selection
Sexual dimorphism
Females and males - Sexual Dimorphism
Females are generally inconspicuous
Makes have more conspicuous markings, structures and behaviours
Reversed sexual dimorphism
Occurs in some species
Honest signals
Indicates favourable alleles that increase chances of survival of offspring
Indicates low parasite burden suggesting a healthy individual
Female choice
Females assessing honest signals of the fitness of males
Lekking Species
Males gather to display at a lek where female choice occurs
Some birds exhibit lekking behaviour
Dominant makes occupy the centre
Satellite males occupy subordinates and juveniles at the fringes
Increases access to females for mating
Success in male-males rivalry through conflict
How will males fight for dominance and access to females
Using elaborate weapons such as antlers, tusks and horns
