Deck 49: Human Impacts on the Biosphere

Question 1

Genes affect the behavior of individuals by ___________.

A) influencing the development of nervous systems
B) affecting the kinds of hormones in individuals
C) governing development of muscles and skeletons
D) all of the above

Answer 1

Genes in any species play a direct role in the development of nervous systems. The products of genes are necessary to construct and operate the sensory receptors, nerves and in complex higher animals, the brain. The gene products thereby play a role in the behavioral responses of the organisms to stimuli. Several hormones (signaling molecules secreted by the endocrine lands ) are also products of some genes. Therefore the answer is
d. all of the above

Question 2

Nazca boobies ( Sula granti ) lay two eggs, several days apart. No matter how much food is available, only one chick survives to adulthood . The first chick to hatch pushes its younger sibling from the nest, and that sibling dies of starvation and neglect. Formulate a hypothesis on how it might be adaptive for parents of this species to lay two eggs if one of the hatchlings tends to kill the other. Design an experiment to test your hypothesis.

Answer 2

The Nazca boobies lay two eggs but the elder hatchling kills the younger one and only one survives to adulthood. And this is independent of the availability of food.
Two eggs are laid instead of one, in order to ensure that even if one egg gets lost by being eaten by predator, or by physical damage, one will survive. However, the fact that only one survives and the other is deliberately killed can be attributed to the fact that the Nazca boobies have to travel sixty miles for fishing and the entire travel consumes two hours, hence the bird can make at the most two trips during the daylight period fetching food for one chick. The other parent has to stay in the nest taking care of the chick. Hence gathering enough food for two chicks is energy expensive. Hence these species have been naturally selected to practice obligate siblicide.
The hypothesis can be tested by growing the chicks separately giving both chicks equal amount of food and then checking their survival.

Question 3

A behavior is defined as adaptive if it __________.

A) varies among individuals of a population
B) occurs without prior learning
C) increases an individuals reproductive success
D) is widespread across a species
E) benefits unrelated members of the species

Answer 3

A type of behavior is called adaptive behavior if it plays a role in perpetuation of that individual's genes. The behavior should lead to either sustenance or increase of its frequency in the population. Hence the answer is
c. increases an individual's reproductive success

Question 4

In 2002 Svante Paabo proposed how one gene, FOXP2 , might have been pivotal in the evolution of language. Humans who have a base-pair substitution in this gene cannot speak intelligibly, understand complex sentences, or make certain movements of the mouth and face.
All mammals have the FOXP2 gene, which has a 715 base-pair sequence. The gene has mutated very little over evolutionary time. The one in chimpanzees differs from the one in mice by a single base pair. But two more base pairs mutated after the ancestors of humans diverged from the lineage that led to chimpanzees. This altered version of the gene became fixed in the lineage that led to modern humans. Why By one hypothesis, language-related traits that arose from the two recent substitutions were favored by directional selection. Speculate on how a capacity to make and comprehend more complex auditory signals shaped the social behavior of the forerunners of humans.

Question 5

Steven Arnold offered slug meat to newborn garter snakes from different populations to test his hypothesis that the snakes response to slugs ___________.

A) was shaped by indirect selection
B) is an instinctive behavior
C) is based on pheromones
D) is adaptive

Question 6

A cheetah scent-marks plants in its territory with certain exocrine gland secretions. What evidence would you require to demonstrate that the cheetah's action is an evolved communication signal

Question 7

Generally, living in a social group costs the individual, in terms of ____________.

A) competition for food, other resources
B) vulnerability to contagious diseases
C) competition for mates
D) all of the above

Question 8

Among primates, differences in sexual behavior tend to be related to the size of a male's gonads. Gorillas have relatively tiny testicles. In a 450-pound male, they may weigh about an ounce. Gorillas live in groups consisting of a male, a few females, and offspring. This is the most typical kind of primate social group. When a female is ready to mate, there usually is only one adult male around to inseminate her.
In contrast, a female chimpanzee advertises her fertile period and mates with many males (Section 49.8). A 100-pound chimpanzee male has testicles about four times as weighty as a gorillas. By making far more sperm, a male chimpanzee increases the odds that his sperm, not a rivals, will fertilize a females egg.
An adult human male is larger than a chimpanzee, but his testicles are only about half the weight. What might this suggest about female promiscuity and male competition to fertilize eggs in the lineage that led to humans

Question 9

Social behavior evolves because ______________.

A) social animals are more advanced than solitary ones
B) under some conditions, the costs of social life to individuals are offset by benefits to the species
C) under some conditions, the benefits of social life to an individual offset the costs to that individual
D) under most conditions, social life has no costs to an individual.

Question 10

In moths and many other insects, potential mates find one another with the help of species-specific pheromones. The pheromones are usually mixes of chemicals derived from fatty acids. Explain how a mutation could result in a change in the mix of chemicals in a moth pheromone. How might such mutations encourage speciation

Question 11

Eusocial insects _________________.

A) live in extended family groups
B) are found among almost all insect orders
C) show a reproductive division of labor
D) a and c
E) all of the above

Question 12

Helping other individuals at a reproductive cost to oneself might be adaptive if those helped are ___________.

A) members of another species
B) competitors for mates
C) close relatives
D) illegitimate signalers

Question 13

Match the terms with their most suitable description.

Question 14

Sexual imprinting is common in birds. During a short sensitive period in early life, the bird learns features that it will seek later, when ready to mate. Figure 49.21 shows an amorous rooster wading into the water after ducks. Speculate on what might have caused this behavior.