BIOL2250_Ecology_07_Life_History_No_Polls

Life History Overview

Focus on various aspects of life history in organisms within the context of ecology and biology.

Phenotypic Plasticity

Definition: Phenotypic plasticity refers to the ability of a single genotype to produce different phenotypes in response to environmental conditions, enabling organisms to adapt to varying environments.Key distinctions:

• Adaptation: Genetic changes that occur over generations in response to environmental pressures.

• Acclimation: Short-term physiological adjustments that occur in response to environmental changes; not genetic.

• Physiological responses: Immediate changes in metabolism or structure without genetic alterations; can enhance survival in changing conditions.

Timing of Seasonal Life History Activity

Shifts in the timing of life history events may not align with changing climate conditions.Example: Snowshoe hare fur changes to white in the winter, but this change in timing has not adapted to the later onset of snowfall, leading to camouflage mismatch and increased predation risk by visual predators.

Sexual or Asexual Reproduction

Meiosis and Budding

• Asexual Reproduction: Polyps reproduce asexually by budding, leading to genetically identical clones.

• Sexual Reproduction: Mature colonies release gamete clusters containing eggs and sperm into the ocean to facilitate genetic diversity.Fertilization Sequence:

1. Sperm fertilizes eggs ->

2. Zygote (fertilized egg) ->

3. Ciliated larva ->

4. Settles and metamorphoses into a polyp.

The Benefit of Sex

Exposure to pathogens increases outcrossing among C. elegans populations, enhancing genetic diversity. Outcrossing rates are higher in populations exposed to pathogens, leading to increased survival rates, as diverse gene pools can better resist diseases.

Sexual Reproduction: Isogamy & Anisogamy

Various modes of sexual reproduction explored, highlighting differences in gamete size and type:

• Isogamy: Gametes of similar size, typically seen in unicellular organisms.

• Anisogamy: Differentiated gametes, where usually male gametes (sperms) are smaller and more numerous, while female gametes (eggs) are larger and provide resources.

The Cost of Sex

Asexual reproduction can rapidly increase numbers, dominating the population in less than ten generations under certain conditions, which can be advantageous but may lead to less genetic variety.

Complex Life Cycles

Involves multiple stages including larval and mature sporophyte stages, depicting intricate life cycles in various organisms.

Processes:

• Description of meiosis and germination in pollen, detailing the reproductive lifecycle from microsporangia to seedlings, showcasing variation in life history strategies.

Trade-offs in Reproduction

Number and Size of Offspring

Smaller clutches of eggs tend to have higher survival rates to fledging, while larger clutches decrease individual survival rates due to resource competition.

Trade-offs Without Parental Care

Plant species with many seeds typically produce small seeds, whereas fewer seed producers generate larger seeds, balancing quantity and quality.

Trade-offs in Current Reproduction

Investing resources in reproduction may reduce individual growth rates or future reproductive success, posing a dilemma for many organisms.

Small Size in Early Life Cycle

Niche Shift:

An organism's ecological role may change as it grows.

Dispersal is highlighted as an important factor in life cycles, especially for marine larvae, influencing population dynamics and genetic spread.

Semelparous vs. Iteroparous

• Semelparous: Organisms reproduce once in their lifetime (e.g., bamboo, salmon) and invest all resources into a single reproductive event.

• Iteroparous: Organisms reproduce multiple times (e.g., most vertebrates) across their lifespan, providing flexibility in reproductive strategies.

R-selection vs. K-selection

• R-selection: Traits favoring rapid reproductive success in low-density populations, typically characterized by high fecundity and low parental investment.

• K-selection: Traits favoring survival and reproductive success in high-density populations, emphasizing parental care and resource management.

CSR Model of Plant Strategies

Competitive, Stress-tolerant, & RuderalHighlights adaptations to environmental conditions in various plant strategies:

• Competitive plants thrive in low-stress, low-disturbance habitats where resources are abundant.

• Stress-tolerant plants can withstand harsh conditions, often at the cost of growth rate or reproductive output.

• Ruderal plants flourish in high-disturbance situations, often opportunistic in colonizing disturbed areas.

Mating Behaviors

Sexual Selection

Mating strategies including monogamy, polygyny, polyandry, and promiscuity, with discussions on parental care and resource control influence reproductive success.

Living in Groups: Benefits and Costs

Advantages of group living enhance access to mates and provides defense against predators. Group foraging improves feeding efficiencies but can lead to increased competition for resources, influencing individual reproductive strategies.

Population Dynamics Definitions

• Population: Group of individuals of the same species in the same area.

• Population Density: Individuals per unit area, often varying with resource availability and habitat conditions.

• Population Size: Total count of individuals in a population, crucial for understanding ecological balance.

Individual Definitions

Genetic Concepts

• Genet: Genetic individual from fertilization, representing the full genetic lineage.

• Ramet: Potentially independent member of a genet, possibly competing for resources, showcasing clonal reproduction.

Measuring Population Size Methods

• Area-Based Counts: For immobile organisms, using sample plots to estimate abundance.

• Distance Methods: For both mobile and immobile organisms, using transects for density estimates.

• Mark-Recapture Studies: Used for moving species, based on capturing, marking, and later recapturing individuals to ascertain population sizes and dynamics.

Distribution and Abundance Terminology

• Endemic: Species restricted to specific regions, often evolved in isolation.

• Native: Species occurring naturally in a region.

• Exotic: Non-native species introduced to an area, often through human activities.

• Invasive: Non-native species that establish and spread, often causing ecological harm and biodiversity loss.

Habitat Suitability Abiotic and Biotic Factors

Factors include moisture, temperature, and food availability; these influence species distribution and are pivotal in habitat conservation strategies.

Metapopulations

Definitions and dynamics of spatially isolated populations interconnected through dispersal patterns, emphasizing the role of habitat fragmentation.

Population Dynamics and Growth Patterns

Four types: exponential growth, logistic growth, fluctuation, and regular cycles, illustrating different population trends based on environmental conditions.

Growth Conditions

Exponential growth conditions relate to immigration changes and environmental factors affecting population size.

Population Cycles and Factors

Population cycles may occur due to internal and external influences, including resource availability, predation, and environmental changes impacting reproduction and survival.

Extinction Risks

Factors include inbreeding, genetic drift, and stochasticity affecting small populations, leading to vulnerability and conservation priorities.

Extinction Vortex

Interconnection of small population size, inbreeding, and genetic factors leading to potential extinction, posing challenges for conservationists.

Recovery Examples

Case studies like the impact of Mnemiopsis and predictions about ecological balance in different ecosystems illustrate resilience and adaptation processes in various species after disturbances.