BIO 305 - Exam II

Life Cycle Graphs

The first step to making a matrix model. Displays the different life stages of an organism as well as its likelihood of reaching said stages.

What do the transitions on life cycle graphs represent?

The change from one life stage to another, represented by arrows in the life cycle graph.

How are life cycle graphs related to transition matrix models?

They’re essentially representing the same data in different ways. Life cycle graphs are visual representations of data while transition matrix models are more mathematical.

What are the steps to a transition matrix model?

1. (1) To get n_1(t+1), start by multiplying the value in the first row, first column of the matrix (P₁₁) by the first element in the vector (n_1(t)) to get P₁₁n_1(t).

1. (2) Then multiply the value in the first row, second column (0) by the second element in the vector (n_2(t)) to get 0.

2. (3) Finally, multiply the value in the first row, third column of the matrix (F) by the third element in the vector (n_3(t)) to get Fn_3(t).

3. (4) Then sum those three products (P₁₁ n_1(t) + 0 + Fn_3(t)) to get n_1(t+1).

Why might transition matrix models be useful in terms of studying population dynamics?

• - Population growth rates

• - Population structure at any time in the future

• - Reproductive value of each age class

• - Sensitivity and elasticity of population growth to changes in probabilities of survival and reproduction

Define: life history theory

the schedule, duration, and amount of energy allocated to key events in an organism’s lifetime. 

Define: life-history traits

the biological characteristics that influence an organism’s schedule of reproduction and survival.

What are some examples of life-history traits?

1. - Age at sexual maturity

2. - Rate of developmental growth

3. - Degree of parental care

4. - Offspring size

Define: senescence

the condition or process of deterioration with age.

What are some examples of life-history tradeoffs?

• - Size vs. number vs. survival of offspring

• - Growth vs. defense vs. reproduction

• - Current vs. future reproduction

• - Sexual vs. asexual reproduction

• - Outcrossing vs. selfing

• - Monogamy vs. promiscuity

Define: masting

Masting is the synchronized, episodic production of large seed crops by a population of plants, followed by years with little or no seed production.

What is the predator satiation hypothesis?

Predator satiation is probably one of the main selective benefits to masting.

How is predator satiation related to the evolution of masting behavior?

When plants produce huge numbers of seeds all at once, predators (like squirrels, birds, insects) can’t eat them all, so more seeds survive to grow into new plants.

Semelparity

reproduce once.

Iteroparous

reproduce multiple times.

How/why might a potential trade-off between mating effort and parental care be related to intrasexual and intersexual selection?

The more offspring an organism creates the less energy it has to invest in each one (principle of allocation). Males and females often differ in terms of their life-history strategies in this regard. Two evolutionary explanations for these differences are differences in the amount of energy invested in (1) the production of gametes and (2) during embryo development. 

This results in an asymmetry in terms of limits to reproductive success: males maximize their fitness by investing most of their energy in mating effort while females are better off investing relatively more of their energy in parental care.

This, in turn, sets the stage for intrasexual and intersexual selection. 

Define: Intrasexual Selection

differential mating success among individuals of one sex due to interactions with individuals of the same sex (e.g., male-male competition for access to mates).

Define: Intersexual Selection

differential mating success among individuals of one sex due to interactions with individuals of a different sex (e.g., female choosiness).

Define: Inclusive Fitness

refers to the fitness of an allele/genotype as measured by the combination of the fitness of the organism bearing it and the fitness of the organism’s relatives who have the same allele/genotype.

Define: Altruism

Altruism is a behavior that benefits another individual (increased fitness or survival) at a cost to the actor’s own fitness.

Why is altruism a paradox?

For Darwin, altruistic behaviors represented a “special difficulty, which at first appeared to me insuperable, and actually fatal to my whole theory.” But he went on to provide a partial solution when he argued that selection could favor traits that result in decreased personal fitness if they increase the survival and reproductive success of close relatives. 

Define: Kin Selection

a type of natural selection that acts through benefits to an organism’s relatives.

Define: Nepotism

favoritism based on kinship.

What are the coefficients of relatedness values between you and one of your parents?

1/2

What are the coefficients of relatedness values between you and a full sibling?

1/2

What are the coefficients of relatedness values between you and a half sibling?

1/4

What are the coefficients of relatedness values between you and one of your grandparents?

1/4

What are the coefficients of relatedness values between you and an aunt or uncle?

1/4

What are the coefficients of relatedness values between you and a first cousin?

1/8

Define: Reciprocal Altruism

refers to a theoretical framework in which the evolution of altruistic behavior among non-kin can be understood. Models of reciprocal altruism can evolve if the recipients reciprocate (so-called tit for tat interactions) The potential benefits of this kind of situation seem clear; however, its fragility also seems clear.

Define: Eusociality

true sociality. Often touted as the epitome of altruistic behavior; it describes organisms with three characteristics:

1. (1) Overlap in generations

2. (2) Cooperative brood care

3. (3) Specialized castes of non-reproductive individuals

Studies suggest that reciprocal altruism is most likely to evolve when:

1. (1) Groups of individuals are relatively stable (individuals tend to interact repeatedly with the same set of individuals).

2. (2) Many opportunities for altruistic behavior occur within an individual’s lifetime (group hunting, defense, foraging, etc.).

3. (3) Individuals have good memories and can differentiate among conspecifics.