Week 26 Flashcards
Life history
The major events relating to an organism’s survival, growth, development, reproduction, and longevity.
Explain the role of limiting resources in allocating time and energy to
different life stages in order to achieve maximum fitness.
Organisms must allocate limited resources (food, water, space, mates, time) efficiently to maximize survival, growth, reproduction, and parental care.
Life history strategies evolve as a response to these resource constraints.
Describe the importance of tradeoffs in the allocation of time and
energy to life history.
Energy used for one function (e.g., growth) cannot be used for another (e.g., reproduction).
Organisms balance investments between survival, reproduction, and parental care.
Different life stages experience different ________. pressures
Different life stages experience different selection pressures (e.g., high juvenile mortality favors producing many offspring).
Summarize the advantages of complex life cycles.
Different life stages can exploit different resources and habitats.
Minimizes risks associated with being small and vulnerable.
Increases evolutionary adaptability.
Apply life history theory to plants using Grime’s CSR scheme.
C (Competitors): Invest in growth over reproduction (e.g., trees).
S (Stress-Tolerators): Survive in harsh conditions (e.g., cacti).
R (Ruderals): Invest in rapid reproduction and colonization (e.g., weeds).
Difference between annuals, biennials, and perennials
Plants are usually categorized by lifespan (& therefore
reproduction):
Annuals: complete their lifespan within one growing season. Semelparous.
Biennials: complete their lifespan over two growing seasons.
◦ Year 1: vegetative growth
◦ Year 2: reproduction
◦ Semelparous.
◦ May have vegetative reproduction too!
Perennials: Live and reproduce over 3 or more years.
Typically iteroparous.
◦ May require several seasons to reach maturity.
◦ May be woody.
◦ May have several modes of reproduction
Name some common tradeoffs in plants
Common tradeoffs:
Competition / Colonization: plants can either be good competitors for light & nutrients (acquire lots of nutrients, grow larger) OR can invest in many seeds with high dispersal and rapid growth/reproduction.
Defence / Growth: Plants can either defend against herbivory, or invest in rapid (re)growth.
Nutrient / Light Competitor: Plants can invest in roots or shoots, but not both at
the same time.
Summarize the fundamental differences in gamete investment and parentage assurance that lead to differences in mating behaviour between males and
females.
Males produce small, cheap sperm; females produce large, costly eggs.
Females invest more in offspring (e.g., pregnancy, lactation), leading to greater mate selectivity.
Males often maximize fitness by mating with multiple females, while females choose high-quality mates.
Define the term sexual dimorphism, and explain why some animals exhibit sexual dimorphism, while others do not
Sexual dimorphism: Differences in physical traits between males and females (e.g., size, coloration, ornaments).
Caused by sexual selection: If one sex is under strong selection for competitive or display traits, dimorphism evolves.
Species with external fertilization or no parental care often lack sexual dimorphism.
Name each of the mating systems, and recognize examples
of each.
Monogamy: One male, one female (e.g., swans, many birds).
Polygyny: One male, multiple females (e.g., lions, deer).
Polyandry: One female, multiple males (e.g., some shorebirds, seahorses).
Promiscuity: No stable pair bonds (e.g., chimpanzees, rabbits).
No functional mating system: Gametes released into the environment (e.g., oysters).
Describe how mating system impacts the proportion of males and females that are reproducing in the population.
In monogamy, equal numbers of males and females reproduce (~1:1).
In polygyny, a few dominant males reproduce with many females, leaving many males without mates.
In polyandry, fewer females reproduce than males.
In promiscuous systems, the reproductive success of individuals varies widely.
Explain how the concept of territories can be applied both to spatial resources, and to mates, and recognize examples of each scenario.
Spatial territories: Defended areas that provide access to food, nesting sites, and resources (e.g., redwing blackbirds, big cats).
Mate territories: Males defend groups of females instead of physical space (e.g., lion prides).
Stronger males control better territories, leading to higher reproductive success.
When does sexual conflict or sexual antagonism occur ?
Sexual conflict or sexual antagonism occurs when the two sexes have conflicting
optimal fitness strategies concerning reproduction. A traitor behaviour that is beneficial for the reproductive success of one sex can reduce the fitness of the other sex
explain difference between r and k selection
**r = “reproductive” organisms
**◦ Short-lived
◦ Few reproductive events
◦ Many offspring
◦ Low parental care
**k = “carrying capacity” organisms
**◦ Long-lived
◦ Several reproductive events
◦ Few offspring per event
◦ High parental care
Organismal Behaviour Must Ultimately Maximize Reproductive Fitness Through…
- Survival
- Growth & Maintenance
- Defense
- Mating
- Parental Care
What are limited resources
factors in the environment which are limited in availability, but necessary for an organism’s
survival, growth, and/or reproductive success.
includes; Food, water, space, mates, TIME
The alloation of resources by an organism to complete its life cycle is called its ….
Life history
Explain an organism energy budget like a bank account
Checking account: energy being used in the present.
◦ Survival
◦ Growth & Maintenance
Savings account: energy that is stored in the body for the future! (fat, muscle,
larger size, etc.
◦ Future growth & maintenance
◦ Defense
◦ Mating
◦ Parental Care
*An individual MUST allocate some of its resources to survival, and growth and/or maintenance at all times.
*
It takes energy and time to acquire resources to make more energy
Each species’ life histrory strategy is based on ……
its probability of survival and reproduction over time.
These determine the organism’s life history traits
List the traits of short vs long lifespan in animals
SHORT
Rapid generation time = rapid
population turnover.
High quantity reproduction
High juvenile mortality; highly
predated
Boom / bust
Rapid adaptation / evolution
Early maturity
Little / no investment in
maintenance, defense
LONG
Slow turnover
Usually smaller, repeated reproduction
events
Parental care increases juvenile
survivorship
Animals may be higher on the food
chain; predators, omnivores.
Later maturity
Slow-growing; may be tolerant of
changing conditions
Most energy invested in survival and
maintenance.
What does reproduction seek to strike ?
Reproduction seeks to strike a balance between Quality and Quantity of offspring:
the highest number of best quality offspring possible given the circumstances at
hand.
Offspring quality vs quantity
QUALITY
Outcrossed, may apply to selfed/cloned.
Genetic: hardier offspring
Genetic: attractive offspring
Passive Parental Care (Provisioning)
◦ Bigger gametes (eggs)
◦ More resources in egg (yolk, starch, etc.)
◦ Larger offspring (more muscle / fat)
Active Parental Care
◦ Feeding
◦ Protection
◦ Teaching
QUANTITY
Cloned, Selfed, or Outcrossed
More opportunities for survival
More opportunities to mate and
reproduce
Smaller offspring tend to disperse
farther
Offspring may escape detection /
predation
Small offspring/propagules can often
be dormant for long periods (dispersal
in time
Name the traits of species who reproudce once or many times
-
Semelparity (reproducing once):
- Organism devotes all its energy into one massive reproductive event.
- Often results in the organism dying right afterward (e.g., some salmon species or certain insects like cicadas).
- Benefit: Maximum offspring produced in one event (high fecundity).
- Risk: If the organism dies before reproducing, it results in no fitness (meaning zero reproductive success). The phrase “Live fast and die young!” highlights this intense but risky strategy.
-
Iteroparity (reproducing multiple times):
- Energy is spread across several reproductive events.
- Benefit: Fitness is spread out over time. Even if one reproductive event fails, the organism still has more chances to succeed. This strategy also allows reproduction to coincide with periods of high resources.
- Risk: Smaller reproductive events compared to semelparity. Additionally, if the organism dies early in life, its overall reproductive success could still be low. The phrase “Slow and steady wins the race!” reflects this less risky, long-term approach.
Both strategies are adaptations to an organism’s environment and life history, balancing energy use, survival, and reproduction. It’s fascinating how nature crafts such diverse reproductive strategies! Do you find one approach more intriguing or relatable
r vs k selection
r = “reproductive” organisms
◦ Short-lived
◦ Few reproductive events
◦ Many offspring
◦ Low parental care
k = “carrying capacity” organisms
◦ Long-lived
◦ Several reproductive events
◦ Few offspring per event
◦ High parental care
Define complex life cycles and metamorphosis
Complex life cycles involve at least two distinct stages that may
have different body forms and live in different habitats.
Transition between stages may be abrupt.
Metamorphosis: Abrupt transition in form from the larval to the juvenile stage.
Why have several separate stages
Each separate life history stages can take advantage of different habitats and resources.
Each life history stage can respond and evolve to selection pressures differently.
Minimizes the drawbacks of small, vulnerable stages in life (juveniles).
Common tradeoffs in plants
Common tradeoffs:
Competition / Colonization: plants can either be good competitors for light &
nutrients (acquire lots of nutrients, grow larger) OR can invest in many seeds with
high dispersal and rapid growth/reproduction.
Defence / Growth: Plants can either defend against herbivory, or invest in rapid
(re)growth.
Nutrient / Light Competitor: Plants can invest in roots or shoots, but not both at
the same time.
Many traits are determined by….
tradeoffs in plants
Competition—biotic competition for limited resources.
Stress—any factor that reduces vegetative growth.
Disturbance—any process that destroys plant biomass.
Sexual selection and conflict, males vs females, and strategy
MALES
Low physical investment; sperm are cheap!
Seldom gestate the young
Can never be “sure” of parentage
STRATEGY
1. Mate with as many females as possible.
2. Ensure parentage; prevent females from
mating with other males.
3. Because parentage not ensured, paternal
care effort is risky.
FEMALES
High physical investment; eggs and
young are expensive.
Often gestate young to some degree;
time and energy required
Effort is wasted if young don’t survive!
STRATEGY
1. Reproduce during high-resource
periods.
2. Choose high-quality males to
improve offspring survival.
3. Invest in maternal care
Since females tend to be more invested and spend more energy during mating…
Females tend to be “pickier” than males.
Females drive mate choice selection.
Most females will successfully mate, while few males will be successful.
Only a few males are actually required to successfully sustain a
population.
Females are attracted to signals of health, implying high male resource acquisition. This implies “good genes.”
Males who exhibit obvious signs of health and vigour will be selected and successfully mate more often than those who do not.
Name all mating system
Monogamy: Males and females form stable pair-bonds for
a mating season, or in some cases, for their reproductive
lives.
Polygamy:
◦ Polygyny: One male has active pair bonds with 2 or more females
◦ Polyandry: One female has active pair bonds with 2 or more males.
Promiscuity: Males and females have no pair bonds
beyond the time it takes to mate.
No functional mating system: gametes are released into
the environment at the same time, fertilization is entirely
random. No mate choice or mate interaction.
What is sex ratio
Sex Ratio is the relative proportions of males vs. females in the population.
The number of females usually has a larger impact on population growth than the number of males.
Only females actually produce offspring!
The Proportion Reproducing is the actual proportion of males or females contributing to population growth.
Mating Systems and Parental Care: Key Factors
LONGEVITY, NUMBER OF OFFSPRING PRODUCED, PARENTAL CARE REQUIRED,
- Longevity
Long-lived species may have more mate fidelity and
parental care - Number of offspring produced
Many offspring = lower fidelity and less parental care - Parental care required
More care required = more fidelity and more offspring
care - Can both parents provide care?
If yes, then males tend to share parental care
Territory
Territory: A plot of habitat, defended by an individual
male (sometimes by a breeding pair), within which the territory holder has exclusive access to food and other limited resources
The territory concept can apply to groups of females, and may or may not include a territorial space in which to access other resources.
Females that are “claimed” by a dominant male may
be more passive than active in their mate choice.
Sexual conflict or sexual antagonism occurs when..
When the two sexes have conflicting optimal fitness
strategies concerning reproduction. A traitor
behaviour that is beneficial for the reproductive success of one sex can reduce the fitness of the other sex
