Ecology Exam 3

Adaptations of Life Histories

morphological, behavioral, and physiological

How do we get Life History Traits?

Adaptations + Environmental Issues = Life History Traits

What are the Life History Traits?

• Growth

• Development: age of sexual maturity

• Reproduction: Fecundity, parity, parental care

• Longevity: senescence

What are species specific life history traits limited by?

• physical constraints

• genetic constraints

• Environmental constraints: time, energy, nutrition, availability

how does natural selection work to shape life histories?

LH traits can be plastic because of natural selection and can be impacted by

• Abiotic stimulations

• Resource Availability

• Predator Presence

Includes photoperiod, temperature, and precipitation that often results from climate change which is why plastic traits do better

Why do LH traits require trade-offs? Name a few.

LH traits require the allocation of limited resources

• Offspring fecundity vs. offspring size, parental care, and parental survival

• Growth vs. age of sexual maturity, longevity, and parity

• Intermediate vs. Determinate growth

• Number of offspring vs. offspring size:

  • Larger seeds = fewer of them

Lack Clutch Experiment Observations

Tropical: 2-3 eggs per nest

High latitudes: 4-10 eggs per nest

More eggs = higher reproductive success

Lack Clutch Experiment Hypotheses

• Parental care is limited by number of offspring

• Latitude affects number of hours of foraging (poles = longer hours in the spring)

• Foraging opportunities impact reproductive success

• Fewer eggs = more parental care

Parental Care vs. Parental Survival

survival may go down the more foraging trips you have to make (there is an optimum number)

In general knowledge for dealing with the growth vs. fecundity tradeoff

Growth vs. Age of maturity and longevity

Larger female = higher fecundity

Growth and reproduction = same assimilated en/nut

Growth and fecundity at expense of next year’s growth and fecundity

Determinate Growth

growth stops at maturity; common in birds and mammals

Indeterminate Growth

growth happens at a decreasing rate; common in fish, herps,and invertebrates

Characteristics of a Long Life

Slow, early growth

Later sexual maturity

Larger female size at maturity

Higher fecundity

Characteristics of a Short Life

Fast, early growth

Early sexual maturity

Higher fecundity

Senescence

A gradual decrease in fecundity and an increase in the probability of mortality. It happens because of an accumulation of molecular defects that fail to be repaired.

Semelparity

quick decline after reproductive maturity

• Inverts, plants, and some fish

Iteroparity

gradual decline

• Vertebrates

• Bet hedging: betting you are going to survive to the next year

What are the effects of climate change for some species

Climate change is causing life activities like eggs hatching, birthing times, and migration patterns to happen earlier than previous times.

• Some organisms are able to adapt to the changing environment (plasticity)

• Others struggle to adapt due to lack of food or timings being off.

Sexual Reproduction

• when progeny inherit DNA from 2 parents through union of 2 gametes

  • Haploid Gametes → Fertilization → zygotes → meiosis → haploid/diploid

Asexual Reproduction

DNA of only one parent

• Vegetative reproduction: clones; occurs in non-sex tissues

• Binary Fission

• Budding: replica of parent that breaks off

• Parthenogenesis

  • Haploid drones: unfertilized egg becomes a drone (honeybees)

  • Diploid eggs: no sperm contribution

    • Clones, partial meiosis

What are the costs of sex

Gonads, Courtship, Mating 

Costs of sex: Gonads

Procreation only (Small portion of total life; lots of energy)

Costs of sex: Courtship

male has to get the attention of the female

• Displays: antlers, feathers, nests, behaviors

• Makes males more at risk, displays aren’t valuable for anything else

• competition with other males; shows dominance

Costs of sex: Mating

resources go directly to mating; males typically lose weight or die by the end of the season

• 2-fold cost of meiosis; loss of 50% of your own genetic material

What are the advantages of sex?

genetic variations

mutations

Red Queen Hypothesis: you’re running fast just to stay where you’re at

Mechanisms of sex determination

• Genetic (gene expression)

  • Binary XY/ ZW

  • Polygenic: certain combinations

  • Hermaphroditism: can be both

  • Haploidiploidy: fertilized vs. unfertilized (honeybees)

• Environmental

  • Hormones

  • Physical (temperature-dependent)

  • Social

  • Parasites

What are the sex ratio adjustment Hypotheses?

Frequency dependent selection

Local Mate Competition

Condition Dependent Selection

Fisher's Frequency Dependent Selection

Sex ratios change

large population

• equal value of male and female

If sexes become unequal between male and female

• Bias at population level

• rarer sex gets more mates, more parental investment goes to rarer sex

Rarer Sex

The sex in a population that has the lesser number of the population

Condition Dependent Selection (Trivers and Willard Hypothesis)

Happens on the individual level

Unequal investment and return

Assumptions

• condition of offspring is correlated to mother

• benefits of parental investment extend into adulthood

• if mom is in good condition, she should have males, if not she will have females because some fitness is better than none (some grandkids are better than none)

Local Mate Competition

local mating means little dispersal

• related males compete for mates

female biased sex ratio

Promiscuity

many mates in a season (mate and move on to the next)

Polygamy

Many of one sex, only one of the other (at least some form of additional interaction

Polgyny

Many females, only one male

Polyandry

many males, only one female

Monogamy

one male and one female

• increased parental care; ensure offspring survival

• Risk not producing by only producing with one partener

mate guarding

monogamous females aren’t always faithful; mate guarding is the only way for males to know it is their offspring

Sneaker males happen in polypairs 

Sexual Dimorphism

difference in outward appearance between males and females 

What are the two causes of sexual dimorphism

Sexual Secondary Characteristics and Sexual Selection

What are the 2 Hypotheses for sexual dimorphism

Sexy sons hypothesis

• females want the “best looking” offspring

Handy Cap Principle

• good general health

• good survival

Runaway Sexual Selection

When selection for preference of a sexual trait and selection for that trait continue to reinforce each other.

• Ex: tail length in birds get longer, the longer the tail, the higher the fitness

• Not ideal for males, inconvenient

Define Social Behavior

Attraction of individuals to one another; can be positive or negative

Purposeful joining

Predator Protection- Advantage

Increased collective vigilance

• individual vigilance vs collective vigilance (safety in numbers)

• decreased predator success

• Increase Feeding (handling time goes down)

Dilution Effect

Confusion Effect

Injuring of Predators: bigger chance of predator being hurt 

Most likely when there are fast attacks or similar size of predators

Dilution Effect

The reduced, or diluted, probability of predation to a single animal when it is in a group

Confusion Effect

confusing predator by moving (flock of birds and hawks)

Why do we not see spitefulness in nature?

spiteful behaviors have no evolutionary strategy; it is uncommon and has no benefit to the donor or recipient