Lecture 7 Flashcards
a record of events relating to its growth,
development, reproduction, and survival.
life history
life history strategy
Is there an optimal strategy?
how quickly to grow, how many offspring, when to reproduce, how often breeding occurs, etc.
timing and division of resources
One genotype may
produce different phenotypes under different
environmental conditions.
i.e. pines in California
phenotypic plasticity
Phenotypic plasticity may produce a
continuous range of growth rates; or “discrete types” known as
morphs
a single genotype
produces several distinct morphs
i.e. toad tadpoles
carnivorous VS omnivorous
bacteriavore morph vs cannibal morph
Polyphenism
Organisms have evolved many different
modes of reproduction.
Asexual reproduction: Simple cell
division—all prokaryotes and many
protists.
Some multicellular organisms reproduce
both sexually and asexually (e.g.,
corals).
Simple cell
division—all prokaryotes and many
protists.
asexual reproduction
Pros and Cons of Asexual VS Sexual Reproduction
Sexually reproducing organisms cannot reproduce as fast
benefit of sexual reproduction:
genetic variation which enables population to survive with a lot of variation in the gene pool (certain individuals may survive disease, drought stress, etc.)
Asexually reproducing organisms have no need to find a mate
involve at least
two distinct stages that may have
different body forms and live in
different habitats
Complex life cycles
Transition between stages may be
abrupt
Abrupt transition
in form from the larval to the
juvenile stage.
Metamorphosis
Reproductive patterns can be categorized
along several continua.
Semelparous species reproduce
only once.
Iteroparous species can reproduce
multiple times.
Semelparous species include:
Annual plants
• Agave—vegetative growth can last
up to 25 years. It also produces
clones asexually.
• Giant Pacific octopus—a female
lays a single clutch of eggs and
broods them for 6 months, dying
after they hatch.
Iteroparous species include:
Trees such as pines and spruces.
• Most large mammals.
_____ and _____ describe
two ends of a continuum of
reproductive patterns.
r-selection and K-selection
r = intrinsic rate of increase. K = carrying capacity
is the intrinsic rate of increase of a
population.
r
is selection for high population
growth rates; in uncrowded
environments, newly disturbed habitats,
etc.
Short life spans, rapid development, early
maturation, low parental investment,
high rates of reproduction.
r-selection
is the carrying capacity for a
population.
K
n is selection for slower growth rates in populations that are at or near K; crowded conditions, efficient reproduction is favored.
Long-lived, develop slowly, delayed
maturation, invest heavily in each
offspring, and low rates of
reproduction.
K-selection
A classification scheme for plant
life histories is based on ____ and _____ (Grime 1977).
stress and disturbance
A classification scheme for plant
life histories:
any factor that reduces
vegetative growth.
stress
A classification scheme for plant
life histories:
any process that
destroys plant biomass.
distrubance
Grime’s Triangular Model
- low stress, low disturbance
- low stress, high disturbance
- high stress, low disturbance
- high stress, high disturbance (excluded)
There are _____ between life history
traits.
trade-offs
Trade-Offs: In species without parental care, reproductive investment is measured as resources invested in \_\_\_\_\_\_\_ (eggs or seeds)
propagules
Size of propagules is a trade-off with ______-
the number of propagules produced
For an iteroparous organism, trade-offs
between current and future reproduction:
i.e. Atlantic cod increase reproductive output
with age.
At 80 cm length, a female produces
about 2 million eggs per year.
At 120 cm, 15 million eggs per year.
Organisms face different selection pressures at
different life cycle stages
Different morphologies and behaviors are
adaptive at different life cycle stages.
Differences in selection pressures over
the course of the life cycle are
responsible for some of the distinctive
patterns of life histories.
i.e. Cod fishing
larger fish harvested a lot more; selective pressure on large cod (artificial selective pressure)
large population of smaller individuals
Life Cycle Evolution
Predation, competition & environment
Life Cycle Evolution
Parental Investment: many forms
i. e. the kiwi
- nutrition and investment into one large egg that occupies the majority of its body
i.e. endosperm
- the nutrient-rich material
that sustains the embryo during
germination (e.g., the milk and meat of
coconuts).
Life Cycle Evolution
Alternative strategy:
movement
(dispersal) - can reduce competition among close relatives and allow for colonization of new areas; can allow escape from areas
with diseases or high predation.
Life Cycle Evolution
State of suspended
animation or dormancy—organisms
can survive unfavorable conditions.
Diapause
Many seeds can survive long dormancy
periods.
Many animals can also enter diapause
Amoeboid protists form a hard
shell or cyst that allows them to
survive dessication.
“Sea monkeys” are brine shrimp
eggs that can survive out of water
for years.
Small size is advantageous for
diapause because less metabolic
energy is needed to stay aliv
Life Cycle Evolution:
For some organisms, one stage of the
life cycle is specialized.
Even in organisms without abrupt shifts
between life stages, different sized and
aged individuals may have very
different ecological roles.
A size- or stage-specific ecological role
has been called an ontogenetic niche
by Werner and Gilliam (1984).
