Reproductive Strategies & Life Tables

Reproductive Strategies

• Semelparous organisms reproduce once before death, as seen in the North Pacific Giant Octopus, which lives 3-5 years
• Iteroparous organisms reproduce multiple times, an example is the Giant Sequoia Tree, which reproduces annually for thousands of years
• The female Kiwi is a crazy organism as it produces one giant egg

Demography

• The statistical study of population change over time

Life Tables

• Used to analyze mortality and survival patterns
• A survivorship curve graphically represents the likelihood of survival to different ages
• Type I curves show high survivorship until old age like humans
• Type II curves show constant mortality rates like birds, rodents, and some reptiles
• Type III curves show high early mortality but low later mortality like fish, plants, and insects

Life History Trade-Offs

• Organisms balance limited resources like time, energy, and nutrients to maximize survival and reproduction

Life History Traits

• These traits affect the probability of survival, reproduction, and growth
• For instance, mice reproduce early, while elephants reproduce much later

Life History Strategies

• The strategies consist of patterns of reproduction, growth, and survival based on resource allocation trade-offs
• Trade-offs are compromises between desirable but incompatible traits

Environmental Constraints

• Environmental factors influence resource allocation
• When food is scarce, Sand Cricket morphs decrease investment in reproduction

r-K Scale

• Natural selection favors individuals that optimize energy and time allocation for reproductive success
• r-strategists prioritize quantity over quality, found in unstable environments such as insects, frogs, fish, weeds, and mice
• K-strategists prioritize quality over quantity, found in stable environments with high competition such as elephants, whales, and humans

r and K Strategies Comparison

• R-adapted species have short lives, rapid growth, early maturity, and many small offspring
• r-adapted species exhibit little parental care or protection, little investment per offspring, and adaptation to unstable environments
• R-adapted species are pioneers/colonizers, niche generalists, prey, and regulated mainly by extrinsic factors
• R-adapted species occupy low trophic levels such as plants and small prey
• K-adapted species have long lives, slower growth, late maturity, and fewer large offspring
• K-adapted species exhibit high parental care/protection and high investment per offspring
• K-adapted species are adapted to stable environments, represent later stages of succession, and are niche specialists
• K-adapted species are predators regulated mainly by intrinsic factors
• K-adapted species occupy high trophic levels and eat predators

Quantitative Traits

• Controlled by many genes with small effects
• Exhibit continuous variation
• Are prone to environmental influence
• Examples of quantitative traits are human height and skin color

Genotypic Variation

• Can cause dramatic differences in phenotypic development related to demographics like birth rate, maturation, body size, and survival

Phenotypic Plasticity

• Variation in phenotypes is caused by interaction between genotype and environmental factors

Life History Traits and Physiology

• Genotype interacts with environment to determine phenotype
• Phenotype interacts with environment to determine performance, fitness
• Individual success determines population life table properties
• Population also influences the environment
• Interactions can cause different evolutionary responses

Life History Traits and Energy Use

• The traits present potential use trade-offs in energy
• Size at birth
• Growth pattern
• Age and size at maturity
• Number, size, and sex ratio of offspring
• Age- and size-specific reproductive investments
• Age- and size-specific mortality schedules
• Length of life

Rate of Living Theory of Aging

• Aging results from accumulated, irreparable cell damage from replication and metabolism
• Repair effectiveness reaches its biological limit
• Aging is a function of metabolic rate
• Aging rate correlates with metabolic rate among organisms
• Species should not evolve longer lifespans because selection for longevity is maxed out

Support for The Rate Of Living Theory of Aging

• Organisms are not expected to expend the same amount of energy per unit mass
• Longer lifetimes can be selected

Telomeres

• Tandem repeat sequences protect chromosome ends
• Telomeres shorten with cell division unless telomerase is present
• Short telomeres trigger p53 production, leading to cell senescence
• Telomere length is inversely correlated with species lifespan
• High p53 levels reduce stem cell division, maintenance, and cancer risk
• Short telomeres reduce cell divisions but also cancer risk

Correlation of Telomeres To Cancer Risk

• Long telomeres lead to low p53, many cell divisions, and high cancer risk
• Short telomeres lead to high p53, few cell divisions, and low cancer risk
• Moderate telomeres are an optimal trade-off with low cancer risk and decent cell divisions

Mutation Accumulation Hypothesis

• Mutations with late-life negative effects accumulate as natural selection weakens
• Mutations harming individuals post-reproduction have reduced impact on fitness
• Weak selection leads to similar fitness, allowing multiple traits to persist

Antagonistic Pleiotropy Hypothesis

• This is where single genes influence multiple traits
• Genes with early-life benefits and late-life detriments are favored by natural selection, because they increase fitness during reproductive years

Reproductive Effort

• The number of offspring in a given year
• David Lack (1947) hypothesized that natural selection maximizes surviving offspring
• British Great Tits have the highest surviving young at a clutch of 12, however the model clutch size is 9, and the mean is 8.5

Trade-Offs

• Energy balances carry over across years
• More eggs in the current year can indicate lower clutch sizes in the next year

Sexual Selection

• Favors traits that increase reproductive success, even at the expense of survival

Sexual Selection Differences

• Sexual dimorphism, or differences between sexes, can be explained by sexual selection
• The dimorphism evolves due to different selective pressures on each sex
• Purple throated caribs display differences due to males and females exploiting different flowers for nectar
• Hollyhock weevil females use long snouts to lay eggs, which males don't need

Bateman and Trivers

• Sexual selection has a more potent effect on males because of the costs of gamete production
• The production of gametes is usually more costly for females regardless of body mass

Case Study: Rough-Skinned Newts

• Sexual dimorphism sees males growing tail crests during breeding season and no parental care
• Parental investment directly relates to gamete production costs
• Most males do not mate or mate with very few females
• Most females mate with multiple males
• Male reproductive success increases with more mates
• Female reproductive success does not change with more mates

Pot Bellied Seahorse

• Males carrying and caring for eggs means that the amount of produced eggs correlates to female body size, males are very choosy

Intrasexual vs Intersexual Selection

• When sexual selection is strong for one sex and weak for the other; members of the strong selection will be competitive
• Where as the members of the weak selection will be choosy

Intrasexual Selection

• Where members of the same sex compete with each other for access to mates, like with lions

Intersexual Selection

• Where individuals of one sex choose mates based on traits, like with the female bird of paradise

Marine Iguanas Example

• Sexual dimorphism shows males are larger
• Males fight for breeding territories
• Larger males get the best territories which leads to higher reproductive success
• Smaller males ejaculate before mating and keep sperm in cloacal pouches

Sperm Competition

• Is when two or more males mate with a female within a short period of time
• The most common adaption is of large quantities of sperm
• Mate guarding, prolonged copulation, copulatory plug deposition, and pheromones exist to reduce attractiveness but damselflies use their barbed horns to remove sperm

Mate Choice

• With intersexual selection, members of the weak selection are choosy
• Here reproductive success is determined by interactions between opposite sexes and long tails are are favored by sexual selection

Female Preference Evolution

• There are five hypotheses; arbitrary preference, pre-existing sensory bias, runaway selection, resource acquisition, and good gene
• Initial female preference may arise by genetic drift, just random fluctuations, not because of survival value

Runaway Selection

• A secondary sexual trait expressed in one sex results because genetically correlated with a preference in another sex
• Cyclic coevolution comes because of female preference for a sexual ornament
• Female preference drives the evolution of deleterious traits which the three spined stickleback fish demonstrates

Female Traits

• These traits also evolve not because of the traits themselves; but because the traits tap into the pre-existing sensory or neural bias

Mites

• Are driven by there tremors and hungry females

Resource Acquisition

• It is favored when mate selection involves female being rewarded with resources that increase fitness like parental care and protection from predators

Good Genes

• Traits that are costly for males that indicate the quality of the males genes

Reproductive Success

• Variation in reproductive success is much more extreme in males than females because males have to fight for mates while those that hold territories have access to more females

Direct Fitness Kin Selection

• Where individuals achieves its own reproduction with or without the help of related individuals

Indirect Fitness Kin Selection

• Where relatives make the additional reproduction possible which can occur through the individuals actions

Siblings

• Brothers, sisters, and offspring all have an r value of 0.5

Grandkids

• Grandkids have an r value of 0.25

Altruism & Cheating

• Promiscuity is common for birds with it being indiscriminate
• Fairy wrens are monogamous but male a pair fathers only 25% of the offspring
• Females will mate with different males which produces half-siblings and full siblings as a result
• Cooperative breeding is also common involving offspring sticking around to help
• Although sexually mature, the offspring are not they dont

Spite

• The close an individuals alle frequency is to the actors, the more related
• Its calculated based on how similar the individual alleles are

B > C

• Where you see you will see spite
• B is less that 0 and A is less than 0 and C Is grate than 0
• In the in equality the negative R * Negative B makes a positive which is what is favored

Sexual Cannibalism

• Increases the male investment in offspring
• The investment increase the production of offspring as reproductive tissues consist of more male-derived amino acids

Eusociality Definition

• Is a group in which is shown an overlap of generation
• They have the non-reproducing adults who cooperative help

3 Hypothesis

• Haplodiploidy, monogamy, and life history is the ecology

Haplodiploid Hypothesis

• In Hymenoptera sister are more related
• Its not widely accepted because
• Not all hymenoptera are eusocial
• Not other test are there to see if the organism display this traits

Monogamy Hypothesis

• Lifetime increase the genetics between sibling
• You could either help you parents and have offspring it up to the cost

Life History Hypothesis

• Is favored where there is present for costly traits
• Leafs cutter ants
• Mole rats

Species Concept

• It defined through its complexity
• It helps understanding the living world

Independent Unit

• Units over through a lot of genetics that have the same kind
• With some over the mutation that make it different
• There are three concept that classify it

Morphospecies

• Usually a look the same or very like
• Its widely applicable especially to plants that can not been classify by other means

Disadvantages

• Its subjective
• It doesnt count towards phenotypic species
• Cryptic

Phylogenetic

• Defined a clade
• Identified threw a lot of evolutionary
• Isolate population
• They are on phylogenetic tree

Interbreeding Species

• Individual that come from the same traits of interbreeding
• This is a mechanism for specification
• It prevent all kinds that are like them
• Mules

Bacteria

• As it is asexual that is the reasion why some think is should be include as part of this concept

Speciation

• It as to be more tested more often
• Can't be tested with fossils
• Difficult assess with geological overlapping

Specification

• Its genetic driven where some of founders

Allopatric SpEciation

• Its a genetic Drift because of continent broken

What is Sympatric

• Where one event effect and the others dont
• The the cromosone start to change where there is both one where the same parents and opposite

Plant

• It high In plants becuase plant dont have that same thing and cant
• Also some may not want to reproduced with the like or dont care

Specification HYBER

• This is where to gene meet so this does not effect them
• All ways hybrid the species by not mixing genes
• The hybirds are effected one of the biggest way by this the genetics change

Reinforcement & Divergence

• Iso or prevent spetification and it result is no to much different then the other
• However, It is affected by what kind of land one is to live in

Stages of SEPC

• It one single trait that is variable
• One type that help keep the same
• Trait where you cant find a match other
• Spec where you can't fined a match at all

Gene Changes

• To help with the new environment
• This help by changing some of the traits and the help
• Over the species over all