Reproductive strategies

what does asexual reproduction show

that sex is not essential to produce offspring

binary fission

a process in which one individual produces a copy of all its DNA, grows to 2x its original size, then splits in two

asexual (or vegetative) propagation

a new plant is produced from the roots, stem, or leaves of a single parent

parthenogenesis

females lay unfertilized eggs, which develop into offspring; can lead to an all female species

what is a major cost of asexual reproduction

if a deleterious mutation is present in a chromosome, all offspring produced would inherit this detriment because offspring are clones of the parent 

true or false: asexual organisms do not undergo recombination or independent assortment

true

What is Muller’s Ratchet

in asexual reproduction, once a mutation evolves in a lineage, it becomes permanent

what does sexual reproduction require

gametes, which are formed during meiosis

what is a benefit of sexual reproduction

once a mutation evolves in lineage, it does not become permanent 

t/f: asexual reproduction avoid muller’s ratchet

false; sexual reproduction avoids this

how is sexual reproduction defined

by a union of gametes

isogamous vs anisogamous

species differ in the size of gametes

isogamy

all individuals within a species produce gametes of the same size (no genetic sexes, but different mating types) 

anisogamy

individuals within a species produce gametes of different sizes (i.e., genetic sexes)

under isogamy, if gametes are the same size, but different types does fertilization occur

yes

under isogamy, if gametes are the same size and the same mating type does fertilization occur

no

under isogamy, gametes from each mating type contain 

DNA, as well as nutrients for developing zygote (yolk)

what is the ancestral state of sexual reproduction

isogamy

in anisogamy gametes are different types and sizes therefore

fertilization occurs

smaller gametes are

mobile, provide no nutrients (DNA only), and can be produced in great number

larger gametes are 

generally immobile, provide essential nutrients for the developing zygotes and are few in number 

anisogamy evolves from isogamy due to

competition

small low investment gametes can be

mass produced and spread far

large immobile gametes ensure

offspring survival and rely on the numerous, mobile gametes to fertilize them

what does anisogamy lead to 

differential parental investment 

pre-fertilization under anisogamy

egg production requires a greater energy investment than sperm production

post-fertilization under anisogamy

gestation or incubating and defending eggs requires much energy. these tasks are generally carried out by females who have already invested more.

under anisogamy natural selection promotes the defense of what sex

women as they invest more than men

how does anisogamy cause males and females to differ

in their potential rate of reproduction 

the difference in the potential rate of reproduction is demonstrated by what

Bateman’s curve 

are males limited when it comes to reproduction

no, due to the production of small cheap sperm males can increase reproductive success by seeking multiple partners

are female limited when it comes to reproduction

yes, by the production of large, expensive eggs. because of this females cannot increase reproductive success by seeking multiple partners per reproductive cycle

what does this graph show

• there is high variation between reproductive success of males, few males are highly success but most males are highly unsuccessful

• there is low variation between reproductive success of females, most females are somewhat successful