Standards - Question 3 (1998)

3. The evolutionary success of organisms depends on reproduction. Some groups of organisms reproduce asexually, some reproduce sexually, while others reproduce both sexually and asexually.

a) Using THREE different organisms, give an example of one organism that reproduces sexually, one that reproduces asexually, and one that reproduces BOTH sexually and asexually. For each organism given as an example, describe two reproductive adaptations. These adaptations may be behavioral, structural, and/or functional.

b) What environmental conditions would favor sexual reproduction? Explain. What environmental conditions would favor asexual reproduction? Explain.

3.a. MAX = 8 points:

(1 for three correct examples; 1 for each adaptation plus 1 possible elaboration point)

Mode of Reproduction

Example Organisms

Two Adaptations with Description

 

(mostly) Sexual

[3 pts max.]

mammals

· compatible genitalia

· external male genitalia

· sex hormones

· internal fertilization

· placental development

· parental care

· gametogenesis
 

flowering plants

· pollen production

· pollen dispersal

· pollen reception by stigma

· endosperm production

· fruit
 

planaria

· fragmentation
 

earthworm

· hermaphroditism
 

many other organisms

· various adaptations

(mostly) Asexual

[3 pts max.]

bacteria

· rapid replication / minimized genome
 

sponge

· fragmentation

· gemmules

· budding
 

planaria

· regeneration
 

hydra

· budding
 

yeast

· budding
 

(some) plants

· vegetative propagation
 

amoebae

· none known
 

various parthenogenetic organisms:

rotifers frogs

turtle fishes

aphids whiptail lizards

· mate independence

· modified meiosis

Both sexual and asexual [3 pts max.]

  

N.B. adaptations can both be sexual, asexual, or one of each.
 

aphids

· parthenogenesis
 

daphnia

· parthenogenesis
 

fungi

· pheromones

· spores
 

planaria

· hermaphroditism
 

some insects (e.g., bees)

· haplodiploidy
 

bacteria

· conjugation

· specialized DNA replication
 

flowering plants (e.g., strawberry)

· runners
 

algae

· adaptations for fragmentation

· zoospores
 

liverworts

· gemmae cups
 

mosses

· protonema fragmentation
 

ferns

· spores

 

 

Standards - Question 3 (1998) (cont.)

 

 

Unacceptable Examples

 

Sexual

Asexual

Both Sexual and Asexual

amoebae

birds

birds

bacteria

earthworms

earthworms

strictly parthenogenetic species

hermaphroditic species

mammals
 

mammals

seastars
 

seastars

  
 

self-fertilizing species

  

 

 

Summary of Point Allocations

 

3a. MAX = 8 points

 

Sexually reproduces (most of the time) ........................................ (3 points)

· example

· adaptation #1 and description ............................................(1 point)

· adaptation #2 and description ............................................(1 point)

· elaboration of one of these adaptations ..........................(1 point)

 

Asexually reproduces (most of the time) ........................................(3 points)

 

· example

· adaptation #1 and description ............................................(1 point)

· adaptation #2 and description ............................................(1 point)

· elaboration of one of these adaptations ..........................(1 point)

 

Sexually and Asexually reproduces ..............................................(3 points)

 

· example

· adaptation #1 and description ............................................(1 point)

· adaptation #2 and description ............................................(1 point)

· elaboration of one of these adaptations ..........................(1 point)

 

Three correct examples ...................................................................(1 point)

 

3b. (MAX = 4 points)

 

Environmental conditions that are ...

· variable favor sexual reproduction ..................................................................................(1 point)

· explanation: sexual reproduction results in offspring diversity ......................(1 point)

· stable and predictable with abundant resources favor asexual reproduction .........(1 point)

· explanation: offspring are produced rapidly and vary little from the parent .(1 point)

· conditions that promote switching to the other mode of reproduction by a particular organism ..............................................................................................................................(1 point)