Biol116 Lecture 5 (10/08/25) (In class)

Fecundity

the number of offspring

(produced by an organism per reproductive episode or the average number of offspring produced by a female at age X.

Parity

the number of reproductive episodes (an organism experiences)

What term describes the proportion of an organism’s total energy budget devoted to reproductive processes?

Reproductive effort

Parental investment

the time and energy given to an offspring by its parents

Longevity (life expectancy)

the lifespan of an organism

Senescence

• a gradual decrease in body condition and fertility and an increase in the probability of mortality

In humans aged 35-85, key bodily functions like metabolism and immune response can decrease by up to what percentage due to senescence?

Up to 65%

Semelparity (parity)

• reproduce only once during their life: 

• ex: cicadas, salmon

Iteoparity

• reproduce multiple times during their life: most animals

“Slow” K life history”

• Long time to sexual maturity

• Long life spans

• Low numbers of offspring

• High parental invesmtnet

• Elephants, oak trees, humans,

“Fast” r life history

• Short time to sexual maturity

• Short life spans

• High numbers of offspring

• Little parental investment

• Fruit flies, weeds

Principle of allocation

• when one life history trait is favored, prevents the adoption of other traits

What is the typical trade-off observed between the number of offspring produced and their individual size?

Producing a higher number of offspring typically results in smaller individual offspring size.

What is the trade-off between the number of offspring and the amount of parental care per offspring?

An increase in the number of offspring generally leads to a decrease in the amount of parental care each one receives.

How does delaying sexual maturity typically trade off with growth?

Delaying sexual maturity allows for more energy to be allocated to growth, often resulting in a larger body size.

In plants, what is the trade-off between the number of seeds produced and their size?

Producing more seeds generally means each seed will be smaller.

In experiments with kestrels, what was the effect of artificially increasing the number of chicks in a nest on the parents' survival?

Increased numbers of chicks led to lower adult survival rates due to the increased effort of hunting for food.

Photoperiod

• the amount of light or number of hours of light that occurs each day providing a cue for many events in the life histories:

• Dormancy, migration, flowering, etc. triggered by

Phenology

periodic plant and animal life cycle events usually influenced by seasonal and inter annual variations in environmental conditions

How does high resource availability affect the timing of metamorphosis in organisms like the barking treefrog?

High food availability allows them to undergo metamorphosis faster and at a larger size.

What global environmental issue has been shown to affect the phenology of various species?

Climate change

Resource vs. Life history

• the fluctuations in resource availability often determine the timing of life history events

Example of effect of predation

• embryos detecting presence of an egg predator, responding by speeding up their hatching time

Disturbance

Temporary change in environmental conditions that causes a change in an ecosystem

• Or process that reduces plant biomass

Stress

• Any biotic factor that limits growth

• Environmental conditions outside the preferred range that challenge an organism’s ability to maintain homeostasis.

The CSR triangle for plants describes three stategies. What do C, S, and R stand for?

Competitive, stress-tolerant, and Ruderal

In the CSR triangle, which strategy describes plants with a superior ability to acquire light, minerals, water, and space?

competitive strategy

In the CSR triangle, which strategy is characterized by slow growth rates, evergreen foliage, and low palatability to herbivores?

Stress-tolerant strategy

Which plant strategy in the CSR triangle involves a short life span, rapid growth, and heavy investment in seed production?

Ruderal strategy

In the context of the 'slow to fast continuum,' 'K' in K life history is related to what ecological concept?

carrying capacity

in the context of the 'slow to fast continuum,' 'r' in r life history is related to what ecological concept?

Maximum reproductive capacity.

In experiments with Pica pica (magpies), what was the effect of adding more eggs to a nest on the number of chicks that successfully fledge (learn to fly)?

Adding too many eggs (e.g., nine) resulted in zero chicks fledging, likely due to increased competition and stress.

Homeostatis

The capacity of organisms to maintain a stable-constant range of internal conditions

(in the face of a wider range of physical and chemical conditions in the external environment)

Competitive (strategy)

• plants with superior ability to acquire light, minerals, water, and space

Stress-tolerant

• Plants may have slow growth rate

• evergreen foliage

• slow rate of water and nutrient use

• low palatability to herbivores

Ruderal

Plants with short life spa, rapid growth rates, heavy investment in seed production.