Life Histories of Marine Organisms Flashcards

Introduction to Marine Ecology and Oceanography

Overview

  • What is a life history?

  • Offspring Number vs. Size

  • Adult survival and reproductive allocation

  • Life history classification

Definitions

  • Life history: A species' lifetime pattern of growth, development, and reproduction.

  • Fitness: Measure of an organism’s reproductive success; those who leave the largest number of mature offspring are considered most fit for their environments.

Trade-offs in Life History

  • Trade-offs: Involves a balance among growth and reproduction; this includes decisions about:

    • Mode of reproduction

    • Age at reproduction

    • Allocation to reproductive number and size of eggs, young, or seeds

    • Parental care

    • Each organism represents a compromise to conflicting demands from differing evolutionary pressures.

Offspring Number vs Size

  • Reproductive success (fitness) is again highlighted; trade-offs exist since organisms have limited energy and resources.

  • There is a trade-off between the number and size of offspring:

    • Producing larger offspring typically results in fewer total offspring.

    • Producing smaller offspring may allow for larger numbers.

Egg Size and Number in Fish

  • Variation in life history traits is pronounced in fish, more than in other animal groups. (Winemiller 1995)

  • Clutch Size: Number of offspring produced per brood varies widely:

    • Example: Mako Sharks produce 2 offspring, whereas an Ocean Sunfish may produce up to 600 million.

Gene Flow and Egg Characteristics

  • Gene Flow: Transfer of alleles or genes from one population to another.

  • Question: How do differences in egg size and number influence gene flow among populations?

  • Discussion on expected genetic differences in darters based on size (small vs. large darters).

Adult Survival and Reproductive Allocation

  • In areas of low adult survival, organisms reproduce earlier and allocate more energy to reproduction.

  • In areas with higher adult survival, organisms delay reproduction and allocate fewer resources to reproduction.

Trade-offs in Resource Allocation

  • Understanding life histories revolves around trade-offs involved in reproductive effort decisions.

  • Resource allocation must maximize an organism’s fitness given time and resource constraints.

Generations and Parenting Decision-Making

  • Breakdown of parental investment considerations, including:

    • Number of large vs. small offspring

    • Proportion of time invested in parental care vs. self-maintenance

    • Frequency of breeding (Parity)

    • Impacts of adult death on longevity and growth rate to maturity

Life History Variation Among Species

  • Gonadosomatic Index (GSI): Calculated as the ovary weight divided by body weight and adjusted for the number of batches of offspring produced annually. (Gunderson, 1997)

Life History Variation Within Species

  • Exploring the potential for life history traits to evolve within species, particularly among different populations affected by varying rates of adult mortality.

Research by Kirk Berschy and Michael Fox (1999)

  • Mature females defined by the presence of yolk in their ovaries.

  • GSI Calculation: GSI = 100 × (ovary mass / body mass)

  • Survival rates from one year to the next ranged from 1 out of 5 to 1 out of 3.

  • Juvenile Survival Analysis: Number of larvae produced compared against 3-year-old fish in the same lake.

Patterns in Life History and Natural Selection

  • The pumpkinseed populations demonstrated that lower adult survival favors the allocation of more resources to reproduction.

  • Research Methodology Questions: Explores choices in study design, such as restricting studies to lakes without major inflows/outflows and what sets the research of Berschy and Fox apart from Gunderson's (1997).

Life History Classification: R and K Selection

  • Classification Framework: Based on a few population characteristics.

  • R-selection: Refers to selection favoring higher rates of population growth (r = racl<em>0TimesextlnR</em>0rac{l<em>0}{T} imes ext{ln} R</em>0).

    • Particularly relevant in newly disturbed habitats where high disturbance continues.

  • K-selection: Refers to selection favoring efficient resource use as populations approach carrying capacity (K).

    • Growth of populations is modeled by the equation: racdNdt=rN(1−racNK)rac{dN}{dt} = rN(1 - rac{N}{K}).

  • Comparison of r and K selection across environments:

    • R selection in variable, unpredictable environments vs. K selection in constant, predictable environments.

Survival Types and Patterns

  • Survival Patterns Across Different Species:

    • R and K-selection patterns observed in human (type I), hydra (type II), and oyster (type III).

Life History Adaptations in Plants (Grime, 1979)

  • Strain of macroalgae and their adaptations based on competition and stress.

Table Analysis of Survival Strategies

  • Opportunistic Forms: Strategies based on rapid colonization, high reproductive capacity, and simple thrall structures designed for high nutrient uptake.

  • Late Successional Forms: More complex life histories, specialized reproductive structures, and greater protection against predation and environmental stress.

Statistical Distribution Patterns

  • Explanation of various population distributions (random, uniform, and clumped) and their respective statistical tests such as the chi-square test for determining significance.

Winemiller & Rose (1992) Life History Dynamics

  • Analysis of life histories with an emphasis on trade-offs between fecundity, survivorship, and reproductive maturity age.

Using Life Histories as a Model

  • Periodic vs. Opportunistic vs. Equilibrium life history strategies and their defining traits.

Differences in Perspectives of Life Histories

  • Influences of size, timing, and the variations in life history classification based on different researchers' focuses.

Size of Offspring and its Developmental Importance

  • Calculating offspring size relative to adult mass and reproductive life span as a measure of species' life history strategies, described mathematically.

Studying Variation Across Groups

  • Charnov (2002) emphasizes developing a life history classification independent of size and time influence and highlights that substantial differences appear among different animal groups while similar groups exhibit less variation.

Example Case Studies of Marine Organisms

  • Mussel (Mytilus edulis): Inputs on reproductive strategies and egg quantity.

  • Silver tip shark (Carcharhinus albimarginatus): Specific details on growth rates and reproductive characteristics.

  • Fish Comparison to Bony Fish (Teleostei): Comparisons on reproductive strategies and lifecycle differences, with details on habitat.

  • Opalascent squid (Loligo opalescens): Lifecycle and spawning behaviors detailed.

Natural Selection and Life Histories

  • Natural selection optimizes strategies according to life cycle stages and the balancing act between offspring survival and reproductive efforts.