Lab Manual - Chapter 1

Question 1

what two interesting features do the immature stages (nymphs) of reduviid bugs display? why?

Answer 1

• cover their thorax with a layer of dust, sand, or soil particles to form ‘dust particles’
• attach dead insects - mainly ants - to their thorax using elastic threads produced by glands on their back to form a ‘backpack’
  -> less likely to be eaten by predators and detected by the bug’s prey

Question 2

class and phylum of insects

Answer 2

class Insects, arthropods

Question 3

define arthropods

Answer 3

animals with jointed legs

Question 4

what is the basic insect body plan?

Answer 4

includes 3 main sections: head, thorax, and abdomen. from the thorax extend three pairs of legs and, usually, one or two pairs of wings

Question 5

where are insects found?

Answer 5

in just about every habitat on Earth. 1.9m species have been identified on earth, over half of which are insects

Question 6

what can an adaptation consist of?

Answer 6

can be a physical feature of the body or a behaviour

Question 7

In each generation, new traits and combinations of traits are created by

Answer 7

mutations and recombination (mixing of genes through sex)

Question 8

which individuals have higher fitness?

Answer 8

individuals that possess traits that help them to survive and reproduce better

Question 9

define fitness

Answer 9

can be measured as the number of offspring an individual produces relative to other individuals in the population

Question 10

describe causes of gene flow

Answer 10

influx of migrants from other population

Question 11

how can we understand the evolutionary process that gave rise to a particular trait and understand whether or not a particular trait is an adaptation?

Answer 11

it is necessary to consult the phylogeny (evolutionary history and relationships) of the species

Question 12

what do biologists do when they observe an interesting trait that appears to be an adaptation?

Answer 12

• come up with at least one hypothesis for how the trait may have increased the fitness of individuals (i.e. its function)
• this is inspired by some knowledge of the organism’s habitat, behaviour, and lifestyle
• test it

Question 13

describe the 2 sections into which adaptations are divided

Answer 13

1. adaptations for viability (success in survival and acquisition of food)
2. adaptations for competition for mates

Question 14

why must hypotheses be tested?

Answer 14

all scientific ideas and explanations are evaluated by how well they conform to empirical evidence

Question 15

what is the name for natural selection arising from variation in viability?

Answer 15

viability selection

Question 16

give examples of adaptations for viability and why they are important

Answer 16

adaptations for:
- locomotion
- predator or parasite avoidance
- food acquisition
- shelter construction
- tolerance of ambient conditions

an individual that fails to survive or obtain food will produce no offspring and have a fitness of 0

Question 17

camouflage

Answer 17

less visible to predator

Question 18

life in water

Answer 18

aquatic insects often have bodies and legs specially shaped to facilitate locomotion (eg oar-like hind legs of the backswimmer)

Question 19

feeding

Answer 19

evolving specialised mouthparts to adapt to particular diets
- ants have powerful jaws = mandibles
- mosquitoes have a tube = stylet
- butterflies have a long tongue = proboscis

Question 20

why are adaptations for competition for mates important?

Answer 20

an individual that fails to mate will produce no offspring and have a fitness of zero.

Question 21

natural selection arising from variable mating success is called

Answer 21

sexual selection

Question 22

what does sexual selection often result in?

Answer 22

the evolution of differences between males and females in secondary sexual characteristics (characteristics other than ovaries and testes)

Question 23

define sexual dimorphism

Answer 23

distinct difference in size or appearance between the sexes of an animal in addition to difference between the sexual organs themselves.

Question 24

why are some fully functional structures in one sex also present in a non-functional (often miniature) form in the other sex?

Answer 24

males and females share nearly all of their genes, so the selection acting on one sex will usually also affect the other sex to some degree

Question 25

what are the two principal mechanisms of sexual selection?

Answer 25

intrasexual competition and mate choice

Question 26

intrasexual competition

Answer 26

• in many species of animals, males fight with other males for access to females
• a male that is able to defeat his rivals in combat will probably sire more offspring
• for this reason, male animals often possess adaptations for fighting (eg horns, modified mandibles, or tusks)

Question 27

mate choice

Answer 27

• mate choice is thought to increase the fitness of the ‘chooser’ by enabling it to mate only with healthy individuals (which are thus more attractive as mates and produce more offspring)
• many animals have adapted to the preferences of the opposite sex by evolving elaborate structures, colour patterns, and courtship displays that may reveal their health and vigour