BIO 331 Exam 2 Questions and Solved Answers 2025

Behavioral defense - -Young animals are often small, naive, unskilled, and less mobile - classic targets of a predator. As a means of offsetting this, parents often will physically/spatially attend to their eggs or hatched/born young in order to defend them from a variety of biotic threats, such as predators and parasites. Among the most common forms of parental care; examples can be found in fish and primates who clean their young of pathogens/parasites to reptiles or amphibians who sit next to their eggs/nest to guard them/it. This form of parenting becomes more difficult in more mobile species, or as young mature and become more mobile. Nutrient provisions - -Parents can invest in young by providing them with nourishment either before hatch/birth (e.g. egg yolk, placenta) or after hatch/birth (e.g. delivering food to them, or mammary milk). This is the most common form of parental care. Even parents who never interact with their offspring after egg-laying or birth typically endow their direct descendants with a nutritional jumpstart (typically egg yolk) - this is true in everything from insects to jellyfish to egg-laying vertebrates. Because live-bearing is less common in the animal kingdom than egg-laying, internal nutrient delivery is less common than external nutrient provisioning. Behavioral transport - -Some young are hatched or born in locations that are not the same as those optimal for their full development, so some parents have evolved to transport their immature, relatively immobile young from one site to another. This form of parental care is most common in oviparous and altricial (meaning very immature young species, i.e. naked, blind, helpless) and less common in viviparous (meaning live-bearing) and precocial (meaning very mature young, i.e. mobile, active) species; this is because animals hatching from eggs or as very undeveloped young require more assistance with movement. Chemical defense - -As an added means of defending young from predators (in addition to behavioral defense), parents may endow their offspring with noxious chemicals that leave them distasteful and unpalatable to potential predators. This requires either a specialized storage or chemoprotective physiological mechanism, so that the chemicals are not toxic to the offspring. This is a common form of very-early life parental investment in insects (e.g. butterfly/moth caterpillars). BIO 331 BIO 331 Environmental regulation - -This is a broad class of parental efforts aimed largely at controlling the abiotic (and occasionally biotic) conditions of development. Examples include site selection, ensuring adequate oxygen concentrations and ambient temperatures, and shielding from weather. Animals requiring very particular environmental conditions for development, or inhabiting environments that have unique high-risk circumstances (e.g. bad-weather threat, low oxygen conditions), commonly will show this form of parental care. Examples span nearly all animal taxa, from oviposition site selection in insects, to egg fanning in some fish, to incubation behavior in birds. Teaching - -A more complex form of behavioral investment in young, in which parents interact repeatedly with offspring to introduce them to proper food sources (search images), habitat, or other behaviors (e.g. song, nest building). Natural selection favors parental instruction when offspring co-exist with parents for a long period of time (i.e. numerous/extended opportunities for learning/reinforcement). This form is also more common among cognitively competent (often vertebrate) species. Recognizing your offspring - -Heterospecific - Right species? Conspecific - Mine? Inter-individual - Which one? Evolution of offspring-recognition signals - -a) vocal (crying, begging) b) visual (patterns) c) olfactory (mammals) d) spatial location What are the main factors that drive the evolution of intricate offspring recognition mechanisms? - -(1) raising young around other species (2) raising young in large groups (3) when some young are more valuable than others (4) when you might mistakenly care for the wrong offspring Playing favorites with offspring - -• Different offspring carry different costs (energy) Different offspring carry different benefits - survival, relatedness, breeding prospects SELECTION TYPICALLY FAVORS PARENTAL FAVORITISM Hypotheses explaining parental favoritism - -1. The silver-spoon hypothesis (i.e. most valued) BIO 331 BIO 331 a. Oldest and/or phenotypically best (based on quality signals) 2. The good-kid hypothesis (i.e. most valued) b. When environmental conditions are challenging (insurancepolicy hypothesis) • Feed them both when (i.e. in case) times are good • Sacrifice one when times are tough • *Siblicide can be an assistive mechanism of brood reduction* c. Sons over daughters (sexy-son hypothesis) • favor the sex with the greater variance in RS 3. The weakness-compensation hypothesis - to equalize the playing field and ensure adequate survival of all young produced (can also be pre- and post-hatch/-birth) - Example: egg yolk hormones 4. The terminal-investment hypothesis - Care most for the last-born/-hatched - With few/no future reproductive prospects What are the driving forces that lead host parents to not reject parasitic young in their nest? - -(1) When the costs of making a mistake (rejecting your own young) are high, (2) When hosts rarely are parasitized (i.e. the history of selection on parasite rejection behavior is brief or weak), (3) When parasitic young very closely resemble a host young (i.e. the host can't tell there is a parasite to reject), (4) When the parasite is small or just one of many offspring being raised (i.e. there is a very small cost to raising that one extra young, whether it's yours or not), (5) When parasites monitor host behavior and retaliate if parasite offspring are rejected. Inclusive fitness - -which is the sum of all genetic contributions from an individual and the genes shared in common with its relatives Hamilton's rule: rB c - -Where r = coefficient of relatedness B = benefits of directing your behavior towards kin c = costs of directing your behavior towards kin If your great-grandparents, great-grandchildren, and cousins are all one additional generation away in relatedness, what if your coefficient of relatedness to them? The correct answer is r = 0.125 (or ⅛), because you multiplied the 0.25 by another 0.5, to get ¼ x ½ = ⅛. BIO 331 BIO 331 Briefly explain two types of fitness cost and two types of fitness benefit of kin-assistance behavior - -Costs = survival risks to group life; lost opportunities of breeding yourself. Benefits = raise more related young than you could alone; increase your mating prospects by demonstrating your worth as a helper Cooperation - -True cooperation is when both parties benefit from an interaction. Because of the mutual fitness advantages to all involved, these types of behaviors are common in the animal kingdom. True altruism - -Altruism is when an actor performs a behavior that incurs a net fitness cost, but that ultimately provides net fitness benefits for the recipient. Because of the net fitness cost to the actor, these types of behaviors are selected against and are very rare. Reciprocal altruism - -Reciprocal altruism is often confused with true altruism. Some behaviors incur an immediate cost to an actor while providing a fitness benefit to the recipient. However, many of these animals have evolved individual recognition and the ability to remember the previous actions of individual