Week 26 Flashcards
(36 cards)
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
