Transcript Sex and behaviour - charlestonbiology

Sex and behaviour
1
Parental investment
 In this section we are learning about the
parental investment in reproduction and
its costs and benefits to organisms and
their evolution
2
Production of gametes
 Sperm
many produced with small energy store
 Eggs
far fewer produced much greater energy
store depends on species
eggs will carry enough energy to allow
young to develop, this limits development
Eggs are a greater investment of resources by
female compared to male sperm
3
Sessile organisms and sex
 Sessile animals are usually
permanently attached to a solid
substrate of some kind, such as a part
of a plant, a dead tree trunk, or a rock
 Many sessile animals, including
sponges, corals and hydra, are
capable of asexual reproduction in
situ by the process of budding.
 Sex cells often released into water to
enable movement and meeting.
4
Sessile organisms and sex
 Plants on the whole can be thought of as sessile.
 They produce gametes such as ova and pollen.
 They rely on distributive mechanisms to move
the pollen such as water, air, insects, birds, bats
and small mammals.
 The reproductive organs will be related to the
form of gametes produced i.e. wind or insect
pollinated flowers are very different.
5
Sexual reproduction
Happens 2 ways
Internally (inside)
The egg is fertilised by sperm inside the female
Mammals, birds, reptiles, insects, spiders
Externally (outside)
The egg is fertilised by a sperm outside the
female
The female lays the eggs and then the male
fertilises them
Fish and some amphibians
Plants and fungi (pollen and spores)
6
Internal fertilisation
Chances of fertilisation is increased
Chances of survival is increased
Zygote forms inside the female body
External fertilisation
Chances of fertilisation is reduced
Produce many eggs as they are laid in water
There is none or very little parental care
7
Parental cost
Reproduction is costly. Individuals are limited in
the degree to which they can devote time and
resources to producing and raising their young,
and such expenditure may also be detrimental to
their future condition, survival, and further
reproductive output.
However, such expenditure is typically beneficial
to the offspring, enhancing their condition,
survival, and reproductive success
8
Parental care
Parental investment can be provided by
the female (female uniparental care),
the male (male uniparental care), or both
(biparental care).
Parents are naturally selected to maximise
the difference between the benefits and the
costs, and parental care will tend to exist
when the benefits are substantially greater
than the costs
9
Fast versus slow
 Fast reproductive strategies are known as
R – strategies
 Slow reproductive strategies are called the
K - strategy
10
r – selected organisms
 Unstable environment, density independent
 Small size of organism
 Energy used to make each individual is low
 Many offspring are produced
 Early maturity
 Short life expectancy
 Each individual reproduces only once
 Type III survivorship pattern in which most of the
individuals die within a short time but few live
much longer
11
K – selected organisms
 Stable environment, density dependent interactions
 Large size of organisms
 Energy used to make each individual is high
 Few offspring are produced
 Late maturity, often prolonged period of parental
care
 Long life expectancy
 Individuals can reproduce more than once in their
lifetime
 Type I or II survivorship pattern in which most
individuals live near the maximum life span
12
13
Type I curves high survival in early and middle life,
followed by a rapid decline in survival in later life.
They are typical of species that produce few
offspring but care for them well, including humans
and many other large mammals.
Type II curves are an intermediate between Types I
and III, where roughly constant mortality rate
experienced regardless of age.
Some birds and some lizards.
Type III curves, the greatest mortality experienced
early in life, with relatively low rates of death beyond
this. Typical of species that produce a large number
of offspring. This includes most marine invertebrates
e.g. oysters (millions of eggs, but most larvae die
from predation or other causes) those that survive
long enough to produce a hard shell live relatively
long.
14
Reproductive strategies
 Reproductive strategies include
monogamy and polygamy
 One mating partner versus many mating
partners
15
Monogamy
 When two animals mate exclusively with
each other or have only one partner
16
Polygamy
 When animals mate with multiple different partners
 Polygyny – when one male mates with multiple
females
 Polyandry – when one female mates with multiple
males
17
Courtship
 Courtship in animals is the behaviour by
which different species select their
partners for reproduction
18
Sexual dimorphism
 The differences in appearance
between males and females of the
same species, such as colour,
shape, size, and structure
19
Sexual dimorphism
 Produced as a result of sexual
selection over many generations
20
Male – male rivalry
Large size or weaponry increases
access to females through conflict.
Some males act
as sneakers to
reproduce.
21
Sexual dimorphism
 Females are generally inconspicuous
 Males have more conspicuous marking,
structures and behaviours
22
Female choice
 Females will assess ‘honest’ signals of the
fitness of males?
 Fitness can be good genes or low parasite
burden?
23
Lekking species
 Taking part in a
communal breeding
display on a lek,
usually birds.
 Hierachy is established
 Dominant males
usually get to mate as
females will choose
them.
 Satellite males may
interfere with process
in hope of mating with
disturbed females.
24
Reversed sexual dimorphism
Reverse sexual dimorphism
is the tendency for certain
bird species to reverse the
normal trend for the male to
be larger than the female.
It is particularly found in birds of prey, for example
the peregrine falcon whose adult male weighs in at
around 660g whereas the female is over 1kg. The
physical size differential is also very obvious.
25
Successful courtship strategies
 Species specific sign stimuli
An external sensory stimulus that triggers a
fixed action pattern
 Fixed action pattern
An instinctive behavioural sequence that is
often very consistent within the species and
almost inevitably runs to completion.
26
Imprinting
 A period of rapid learning that occurs during a
brief receptive period, typically soon after
birth or hatching
 It establishes a long-lasting behavioural
response to a specific individual or object, as
attachment to parent, offspring, or site. It is
likely to influence mate choice later in life.
27