Ecology Quiz 4 Flashcards
What is life history?
Life history characteristics include:
The life history strategy of a species is
An organism’s life history is a record of events relating to its growth, development, reproduction, and survival
Life history characteristics include:
Age and size at sexual maturity
Amount and timing of reproduction
Survival and mortality rates
The life history strategy of a species is the overall pattern in the average timing and nature of life history events
Life History Diversity
Natural selection
Within a species, individual strategies may differ
because of genetic variation, environmental conditions, or both
Natural selection favors individuals whose life history traits result in their having a better chance of surviving and reproducing (fitness).
Allocation of resources
Resources are BLANK meaning:
Allocation:
Population growth rate:
Energy and resources are finite and must allocate that to these different functions - Limiting Factors:
Resources are finite - Resources are limited so if you allocate X units of energy to reproduction it means those same X units can’t also be used for growth.
Allocation: The relative amounts of energy or resources that an organism devotes to different functions
Population growth rate: number of individuals in a group of organisms of same species
Energy and resources are finite and must allocate that to these different functions - Limiting Factors: Growth, Reproduction, Survival
Trade Offs:
Example - survival rate times fecundity(how much offspring will produce)
Trade Offs: “an evolutionary dilemma whereby genetic changes conferring increased fitness in one circumstance inescapably involves sacrifice of fitness in another” (Grime 2001) - Trade off is a negative relationship in a plot
Why bird species produce more offspring would have less chances of survival because they are allocating resources to the offspring rather than putting resources to something else. Larger egg means mother invests more into one egg, more egg less resources to allocate.
Tradeoffs among growth, reproduction, survival:
Time, energy and nutrients allocated to one purpose cannot be used for another:
- Current reproduction may lower survival and future reproduction.
- Current growth may lower or delay reproduction.
- Investments in defense may lower future reproduction.
By allocating resources to reproduction instead of growth, individuals reproduce at a smaller size. - growth and reproduction trade off
Phenotype is manifestation of genotype:
Phenotype is manifestation of genotype ie what it looks like
One genotype produces different phenotypes under different environmental conditions.
Phenotypic plasticity may result in a continuous range of sizes; or discrete types called morphs.
Timing of seasonal life history activities can be of critical importance.
Asexual reproduction:
Benefits:
Cons:
Asexual reproduction: Simple cell division (binary fission)—all prokaryotes and many protists also in plants - genetically the same and sexual is recombination
Benefits: asexual
Fast
Requires less energy
No courtship needed
Cons: asexual
Does not contribute to genetic diversity
Changing environment presents issues to the organism if genetic diversity is low
Sexual reproduction:
Isogamy:
Anisogamy:
Benefits:
Cons:
Sexual reproduction: Most plants and animals and many fungi and protists reproduce sexually. Production of gametes which is haploid. Most plants and animals and many fungi and protists reproduce sexually.
Isogamy: Gametes are equal in size.
Anisogamy: Most multicellular organisms produce gametes of different sizes; the egg is usually much larger and contains nutritional material.
Benefits: Sexual reproduction
- Recombination promotes genetic variation
- Better ability of populations to respond to environmental challenges.
- C. elegans individuals are either male or hermaphrodite.
- Hermaphrodites can reproduce by self-fertilization (selfing) or mating with males (outcrossing).
Cons: Sexual reproduction
- An individual transmits only half of its genome to the next generation
Slow
- Population growth rate is only ~ half that of asexually reproducing species.
- Recombination and chromosome assortment during meiosis can break up favorable gene combinations
Reproductive tradeoffs
Lack clutch size:
David Lack Hypothesis + Experiment:
Species without parental care:
Lack clutch size: Maximum number of offspring a parent can successfully raise to maturity.
David Lack (1947) noticed bird’s clutch size increases with latitude
Hypothesis: longer daylight hours may allow parents more time to forage and feed more offspring
Experimental manipulation of clutch size in lesser black- backed gulls showed that in larger clutches, offspring have less chance of survival (Nager et al. 2000).
In species without parental care, resources are invested in propagules (eggs, spores, or seeds).
- Size of the propagule is a trade-off with the number produced.
- In plants, seed size is negatively correlated with the number of seeds produced.
Life Cycle Evolution:
Complex life cycles:
Metamorphosis:
Functional specialization of stages is common in BLANK
Example:
Paedomorphic means?
Many plants, algae, and protists also have complex life cycles: Plants and most algae have alternation of generations:
Different morphologies and behaviors are adaptive at different life cycle stages.
Differences in selection pressures over the course of the life cycle are responsible for distinctive patterns in the life histories of organisms.
Complex life cycles: At least two stages with different body forms that live in different habitats and eat different foods. - Complex life cycles are common in insects, marine invertebrates, amphibians, and some fishes.
Metamorphosis: Abrupt transition between larval and juvenile stages.
Functional specialization of stages is common in complex life cycles.
In many insects the larval stage is specialized for feeding and growth; the adult is specialized for dispersal and reproduction.
Larvae may also have spines, bristles, or other structures to deter predators.
Example: If the larval habitat is very favorable, metamorphosis may be delayed or eliminated.
Some salamanders mature sexually while retaining larval morphology and habitat (paedomorphic).
Mole salamanders have both aquatic paedomorphic adults and terrestrial metamorphic adults in the same population.
Frequency of paedomorphosis depends on factors such as predation, food availability, and competition, which influence survival and growth in the aquatic habitat.
Many plants, algae, and protists also have complex life cycles:
Plants and most algae have alternation of generations: a multicellular diploid sporophyte alternates with a multicellular haploid gametophyte
Parental investment:
Parental investment:
* Provisioning eggs or embryos—yolk and protective coverings for eggs, nutrient-rich endosperm in plant seeds
*Parental care—invest time and energy to feed and protect offspring
Small early life stages are vulnerable to predation and competition for food, but small size can allow early stages to do things that adult stages cannot.
Organisms have various mechanisms to protect the small life stages.
Dispersal
Propagules:
Movement of organisms or propagules from their birthplace.
Small offspring are well-suited for dispersal.
Dispersal can reduce competition among close relatives, allow colonization of new areas, or escape from areas with diseases or high predation.
Propagules: (eggs, spores, or seeds)
any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism.
Dormancy
State of suspended growth and development in which an organism can survive unfavorable conditions.
Small seeds, spores, eggs, and embryos are best suited to dormancy—less metabolic energy is needed to stay alive.
Some larger animals also enter dormancy
Number of reproductive events
Semelparous/Semelparity VS Iteroparous
Iteroparous species: can reproduce multiple times; most animals, many kinds of plants.
Iteroparity: repeated reproduction during lifespan
- Spreads reproductive chances across multiple time points.
- Only a portion of lifetime reproductive effort is invested into any given reproductive event.
- Avoid “putting all your eggs in one basket”.
Semelparous/Semelparity: reproduce only once - example:
Annual plants
Agave produces seeds once, also produces clones
Giant Pacific octopus
If there is a low probability of survival following reproduction:
Current reproductive effort should be maximized.
This may lead to even lowered survival probability and a single reproductive episode.
Hypotheses for the evolution of semelparity
- Three
- Environment frequently disturbed:
Reduces adult survival
Allocated to reproduction before death.
Desert annuals, some insects, small mammals - Pollinator attraction:
Arid lands, widely spaced plants.
Massive floral display was needed to attract pollinators. - Environment limits rapid growth:
Multiple seasons needed to gain enough energy for reproduction:
- High altitude plants with a short growing season.
- Coupled with pollinator attraction.
