Natural Resources Ecology - Chapter 8: Life Histories

Flashcards covering key concepts from RNR 316 Natural Resources Ecology, Chapter 8 on Life Histories, including evolution, r/K selection strategies, Grime's CSR triangle, and environmental influences on life history traits.

What are the two main ways evolution can occur?

Evolution can occur through random processes or through selection.

At what taxonomic level does microevolution operate, and at what level does macroevolution operate?

Microevolution operates at the population level, while macroevolution operates at the species level and higher levels of taxonomic organization.

What defines an organism's life history traits?

Life history traits represent the schedule of an organism's life and are shaped by trade-offs.

What is the 'tradeoff in allocation' in an organism's life history?

The tradeoff in allocation refers to how an organism invests its time and energy between growth, reproduction, and survival for maximum fitness.

What are the typical fecundity, number of reproductive episodes (parity), and parental investment for an Emperor Penguin?

Emperor Penguins typically have a fecundity of 1, 7-9 reproductive episodes (parity), and 5 months of parental investment.

Describe the key characteristics of a 'K-selected' life history strategy.

K-selected species have a long time to sexual maturity, long life spans, low numbers of offspring, and high parental investment, often with traits that increase competitive ability.

Describe the key characteristics of an 'r-selected' life history strategy.

r-selected species have a short time to sexual maturity, short life spans, high numbers of offspring, and little parental investment, often with traits that increase population growth rate.

Provide an example of a K-selected plant and one of its contributing traits.

Oak trees are K-selected due to their longevity, late maturation, large size allowing them to compete for sunlight, and production of big, energy-rich seeds.

Provide an example of an r-selected plant and one of its contributing traits.

Dandelions are r-selected because they are short-lived, produce many small, wind-dispersed seeds, and have little parental care.

What is secondary succession, and which type of species typically colonizes a disturbed site first?

Secondary succession is the change in communities after a disturbance removes the stable community. Seedlings of r-selected species, adapted to open sites, are the first to colonize.

Name the three plant life history strategies in Grime's CSR triangle and which of these are typically K-selected or r-selected.

The three strategies are Competitors (C), Stress-tolerators (S), and Ruderals (R). Competitors and Stress-tolerators are usually K-selected, while Ruderals are usually r-selected.

What general relationship is observed between the number of seeds produced by a plant and the average mass of those seeds?

Plants that produce a larger number of seeds generally produce smaller seeds, demonstrating a trade-off.

How does an increase in offspring number often affect the amount of parental care per offspring and, consequently, offspring survival?

As the number of offspring increases, the amount of parental care per offspring tends to decrease, which can reduce the chances of offspring survival.

Differentiate between semelparity and iteroparity in reproduction.

Semelparity involves a single, 'big bang' reproductive episode (costly reproduction), while iteroparity involves multiple reproductive episodes ('bet hedging') spread over an organism's life.

Why do periodical cicadas emerge synchronously after 13 or 17 years underground?

Synchronous emergence is likely a strategy to overwhelm potential predators through sheer numbers.

What is senescence in the context of an organism's life history?

Senescence is a gradual decrease in fecundity and an increase in the probability of mortality, often considered an inevitable consequence of natural wear and tear.

How does photoperiod influence life history events in organisms?

Photoperiod (the amount of light each day) provides an important environmental cue for many life history events, such as the timing of diapause.

How can the presence of predators influence the life history traits of organisms like freshwater snails?

When predators are present, freshwater snails may delay reproduction to grow larger, which allows them to produce more eggs per clutch and live longer once they start reproducing, achieving similar lifetime fecundity.

How have commercial fisheries influenced the life history traits of fish like the Northeast Arctic cod?

Commercial fisheries, by harvesting the largest individuals, have imposed selection pressure that has led to a decrease in the average age at maturity for species like the Northeast Arctic cod.

What is a 'phenological mismatch' and how can it impact populations?

A phenological mismatch occurs when the timing of ecological events (e.g., breeding, food availability) shifts disproportionately due to climate change, which can lead to population declines if organisms cannot adapt to the new timing.