BIOLOGY 181 PRACTICE EXAM 2025/2026 QUESTIONS AND
ANSWERS GRADED A+
✔✔(5) How are invasive species introduced? - ✔✔A. Often intentional introductions
(crops, ornaments, animals)
B. Accidental introductions (insect and animal pests, weeds, diseases)
✔✔(5) Why do some species become invasive and not others? - ✔✔A. The invasive
species have a lack of coevolutionary history with their new environment. This means
they often lack natural predators/diseases, their prey has no defenses against them,
and because of these factors they are superior competitors.
B. Life history characteristics like rapid reproduction, high fecundity, rapid dispersal,
broad diets, adaptability, tolerance of human disturbance leads some to become
invasive.
Ex: European rabbit introduction to Australia and rapid reproduction
✔✔(5) What are the ecological/evolutionary impacts of invasives? - ✔✔A. Parasitism
(ex: invasive mite on honeybees introduced in 1987, 30-80% losses of hives,
exponential growth in mites)
B. Predation (ex: Nile perch in Lake Victoria, half of cichlids now extinct due to
introduction of invasive perch in 1954)
C. Competition (ex: Fire ants vs. native ants, 1940s introduction, rapid reproduction
(multiple queens--polygynes), 60% reduction in native ants where fire ants occur)
D. Selection on native species (ex: cane toads in Australia impacts snake's body length
and head size because it is poisonous for them)
✔✔(5) What can be done about invasive species? - ✔✔Most promising--legislative
prevention
White lists: burden of proof on importer (cost of invasives from taxpayers to the
corporations bringing them in)
✔✔(6) What is a fertility rate? - ✔✔The average number of children born per woman.
✔✔(6) Has food influenced human evolution? If so, how? - ✔✔Yes.
- Progressive increase in human size until 1.8 MYA
- Progressive decrease in size DIFFERENCE between males and females.
✔✔(6) What are two hypotheses for humans increasing in size? - ✔✔1. There was a
shift from trees to the ground, which favored enhanced mobility to search for food and
increase range.
, 2. New foods (more meat) combined with more food supported larger body size
✔✔(6) Why did sexual dimorphism decrease? (3 hypotheses) - ✔✔1. Reduction of
male-male competition (unlikely when looking at modern tribes)
2. Fertility selection for female size (large moms are better able to carry offspring, have
larger offspring which are more likely to survive)
3. Reduction of food competition due to a broader niche
✔✔(6) Why did agriculture "evolve"? - ✔✔1. Decline in availability of animals due to
extinctions (Pleistocene, for instance)
2. Increased technology for food harvest and storage (think sickles, mortar and pestles,
underground storage, roasting which prevented seeds from sprouting)
3. Increased availability in annual crops because of climate changes during the
Pleistocene period
4. Rise in the size of the human population and wide food shortages
✔✔(6) How has agriculture impacted human evolution? - ✔✔1. Shortened birth interval
(not being on the go means humans can have children more often)
2. Food surpluses necessitate food storage and guarding
3. Some division of labor is possible
4. Clothing, blankets, nets, ropes, transport
5. Animal domesticated enhanced transmission of diseases from animals to people
✔✔(6) How did our food evolve? - ✔✔Unconscious selection: humans preserve most
valuable and destroy less valuable w/o any thought of altering the organism to some
preconceived goal
Humans unconsciously selected for...
1. Larger seeds and fruits
2. Loss of dispersal mechanisms in crops (a pain when farming)
3. Loss of dormancy
4. Loss of outcrossing
ANSWERS GRADED A+
✔✔(5) How are invasive species introduced? - ✔✔A. Often intentional introductions
(crops, ornaments, animals)
B. Accidental introductions (insect and animal pests, weeds, diseases)
✔✔(5) Why do some species become invasive and not others? - ✔✔A. The invasive
species have a lack of coevolutionary history with their new environment. This means
they often lack natural predators/diseases, their prey has no defenses against them,
and because of these factors they are superior competitors.
B. Life history characteristics like rapid reproduction, high fecundity, rapid dispersal,
broad diets, adaptability, tolerance of human disturbance leads some to become
invasive.
Ex: European rabbit introduction to Australia and rapid reproduction
✔✔(5) What are the ecological/evolutionary impacts of invasives? - ✔✔A. Parasitism
(ex: invasive mite on honeybees introduced in 1987, 30-80% losses of hives,
exponential growth in mites)
B. Predation (ex: Nile perch in Lake Victoria, half of cichlids now extinct due to
introduction of invasive perch in 1954)
C. Competition (ex: Fire ants vs. native ants, 1940s introduction, rapid reproduction
(multiple queens--polygynes), 60% reduction in native ants where fire ants occur)
D. Selection on native species (ex: cane toads in Australia impacts snake's body length
and head size because it is poisonous for them)
✔✔(5) What can be done about invasive species? - ✔✔Most promising--legislative
prevention
White lists: burden of proof on importer (cost of invasives from taxpayers to the
corporations bringing them in)
✔✔(6) What is a fertility rate? - ✔✔The average number of children born per woman.
✔✔(6) Has food influenced human evolution? If so, how? - ✔✔Yes.
- Progressive increase in human size until 1.8 MYA
- Progressive decrease in size DIFFERENCE between males and females.
✔✔(6) What are two hypotheses for humans increasing in size? - ✔✔1. There was a
shift from trees to the ground, which favored enhanced mobility to search for food and
increase range.
, 2. New foods (more meat) combined with more food supported larger body size
✔✔(6) Why did sexual dimorphism decrease? (3 hypotheses) - ✔✔1. Reduction of
male-male competition (unlikely when looking at modern tribes)
2. Fertility selection for female size (large moms are better able to carry offspring, have
larger offspring which are more likely to survive)
3. Reduction of food competition due to a broader niche
✔✔(6) Why did agriculture "evolve"? - ✔✔1. Decline in availability of animals due to
extinctions (Pleistocene, for instance)
2. Increased technology for food harvest and storage (think sickles, mortar and pestles,
underground storage, roasting which prevented seeds from sprouting)
3. Increased availability in annual crops because of climate changes during the
Pleistocene period
4. Rise in the size of the human population and wide food shortages
✔✔(6) How has agriculture impacted human evolution? - ✔✔1. Shortened birth interval
(not being on the go means humans can have children more often)
2. Food surpluses necessitate food storage and guarding
3. Some division of labor is possible
4. Clothing, blankets, nets, ropes, transport
5. Animal domesticated enhanced transmission of diseases from animals to people
✔✔(6) How did our food evolve? - ✔✔Unconscious selection: humans preserve most
valuable and destroy less valuable w/o any thought of altering the organism to some
preconceived goal
Humans unconsciously selected for...
1. Larger seeds and fruits
2. Loss of dispersal mechanisms in crops (a pain when farming)
3. Loss of dormancy
4. Loss of outcrossing
