Download Sexual Reproduction, Mating Systems and Parenting

Essential Concepts – Sexual Reproduction, Mating Systems and Parenting
Obj 1 Contrast sexual and asexual reproduction.
Condition
Individual’s genes
passed
Courtship
Asexual
Reproduction
100%
none
Resources used
just the essentials
Diverse offspring
low. Mutation
only
high
Offspring
adaptability to current
environment
Offspring
low
adaptability to
changing
environment
Effect of harmful
high
mutation
Sexual Reproduction
“Winner”
50%
Asexual
energy demanding and
increases chance of being
killed
many sperm wasted, many
males never fertilize eggs
high. Mutation and gene
recombinations
some high, some less
Asexual
some high, some low
Sexual
decreases and hides harmful
mutation (recessive genes)
Sexual
Asexual
Depends,
see below
Asexual
Obj 2 Describe what prompts mating behavior in animals
Climate-Hormonal Interactions
Cues such as photoperiod (ratio of night and day), temperature, rainfall, food availability,
etc., affect the hormone levels, and thus the mating behavior, of many animals. For
example, many birds become sexually active when days get significantly long.
Social-Hormonal Interactions
Being near others may initiate mating behavior. For example, when a male ring dove is
present, a female’s progesterone level increases, which then leads to courtship behavior.
Also being near females in estrus (heat) causes males to initiate mating behaviors, as in
dogs and some apes.
Obj 3 Explain how sexual selection can be considered an evolutionary tool.
Sexual selection involves processes that lead to some individuals being more successful at
having access to mates and being able to pass on genes.
Two types of sexual selection:
 Intersexual Selection (between the sexes). One sex chooses another sex, the latter
often having to advertise. Examples: a peacock’s feathers attract mates, male
bowerbirds build fancy structure.
 Intrasexual Selection (within a sex). Competition within one sex to gain access to the
other sex. Examples: male deer fight during breeding season to gain access to females,
in many insects a male will scoop out the sperm of a previous suitor, in some animals a
male deposits a “copulatory plug” that decreases the chance that sperm from another
male will fertilize eggs.
Obj 4 Compare and contrast different mating systems.
Monogamy – one male and one female pair for at least one season and cooperate in
rearing offspring. Advantages: decrease time to find mate. Common in birds.
Polygyny – one male has access to more that one female. The male usually defends the
territory and females raise the young. Common in mammals, like seals.
Polandry – one female has access to more than one male. This situation is very rare. The
female defends the territory and male cares for the young. Example: phalaropes, a type of
shorebird.
Obj 5 Describe how ecological factors influence parental care.
“K-selected” species, like humans and elephants, have few young but invest a lot in each
one. High quality young, rather than a high quantity of young, result. Individuals of such
species often live in stable habitats with intense competition within the species.
Prolonged dependency and extensive parental care are also favored when a species
depends on food that is scarce and difficult to obtain. Wolves and lions come to mind.
In addition, for species that have flexible behaviors which are largely shaped by learning
(old world monkeys and humans), intense parental investment is necessary.
“R-selected” species, like flies, frogs and salmon, produce many offspring at a time and
invest little or nothing in their care. Animals that employ this strategy are adapted to
fluctuating environments with high mortality rates.