BiologyII OpenStax Worksheets
Worksheet with Questions
What is speciation?
What is allopatric speciation?
What is dispersal?
What is vicariance?
What is an example given in class of allopatric speciation?
What is sympatric speciation?
What is aneuploidy?
What is nondisjunction?
What are the two main types of reproductive isolation?
What is a prezygotic barrier?
What is a postzygotic barrier?
What is Temporal Isolation?
What is habitat isolation?
What is behavioral isolation?
What is gametic isolation?
What is structural isolation?
Chapter 18 Worksheet with Both Questions and Sample AnswersWhat is speciation?
What is speciation?
- formation of 2 species from 1 original species
What does “allo-” mean?
- "other"
What does “-patric” mean?
"homeland"
What is allopatric speciation?
• involves geographic separation of populations from a parent species and subsequent evolution
What is an example given in class of allopatric speciation?
• Example 1:
– The Northern Spotted Owl and the Mexican Spotted Owl inhabit geographically separate locations with different climates and ecosystems
– The owl is an example of allopatric speciation via dispersal
• In the north, the climate is cooler than in the south
• Types of organisms in each ecosystem differ, as do their behaviors and habits
• Hunting habits and prey choices of the southern owls vary from the northern owls
– These variances can lead to evolved differences in the owls, and speciation likely will occur
· Example 2: Adaptive Radiation
o From an original founder species of bird, separated via allopatric speciation, multiple bird species evolve with distinctive differences in the species’ beaks
o Natural selection allows specific food sources in each new habitat to evolve a different beak suited to the specific food source
§ Nihoa: thicker, stronger beak which is suited to break hard nuts
§ Apapane, Liwi, & Amakihi: long beaks to dip into flowers to reach the nectar
§ Maui & Akiapol’au: beaks like swords, appropriate for stabbing and impaling insects
What is a cute way to remember allopatric speciation involves geographic separation from a parent species?
· Have you ever seen the TV show “Sponge Bob Square Pants”? Do you remember the sea star named Patrick? Patrick has been geographically separated from all the other sea stars in the sea. Imagine Sponge Bob Square Pants walking up to Patrick and saying (wave hand in hello greeting motion), “ ‘Allo Patrick!” (sounds like Hello Patrick! Or ‘ello Partic! with a British accent). So much for Patrick making more little sea stars via sexual reproduction while he is geographically separated from all the other sea stars; he will have to resort to asexual reproduction
What is dispersal?
• when a few members of a species move to a new geographical area
– Example: 2 flying insect populations take up residence in separate nearby valleys → individuals from each population would likely fly back and forth continuing gene flow
What is vicariance?
• when a natural situation arises to physically divide organisms
– Example: 2 rodent populations become divided by the formation of a new lake, making continued gene flow unlikely
What does “-sym” mean?
"same"
What is sympatric speciation?
• involves speciation occurring within a parent species remaining in 1 location.
• Def: Species divergence with no physical barriers in place to separate individuals who continue to live and reproduce in the same habitat
• Sympatric speciation can begin with a serious chromosomal error during cell division
• Normal cell division: chromosomes replicate, pair up, and then separate so that each new cell has the same number of chromosomes
What is aneuploidy?
· Aneuploidy results when the gametes have too many or too few chromosomes due to nondisjunction during meiosis. In the example shown here, the resulting offspring will have 2n+1 or 2n-1 chromosomes
Aneuploidy
What is nondisjunction?
• aneuploidy caused by chromosome pairs that fail to separate, resulting in gametes that have too many or too few chromosomes
What are the two main types of reproductive isolation?
• Prezygotic barrier
• Postzygotic barrier
What is a prezygotic barrier?
• mechanism that prevents fertilization or blocks reproduction from taking place
What is a postzygotic barrier?
· organisms do not survive embryonic stages, are born sterile, or show greatly reduced fitness & failure to thrive
What is Temporal Isolation?
· Many organisms only reproduce at certain times of the year, often just annually. Differences in breeding schedules, called temporal isolation, can act as a form of reproductive isolation.(a) (species of frog) Rana aurora breeds earlier in the year (Jan – Mar) than (b) (other species of frog) Rana boylii (March – May).
What is habitat isolation?
· A cricket population that was divided after a flood could no longer interact with each other. The cricket (a) Gryllus pennsylvanicus prefers sandy soil, and the cricket (b) Gryllus firmus prefers loamy soil. Over time, the forces of natural selection, mutation, and genetic drift will likely result in the divergence of the 2 groups because of their different soil preferences, causing them to be genetically isolated.
What is behavioral isolation?
• Behavioral isolation occurs when the presence or absence of a specific mating behavior or display prevents reproduction from taking place
• Example: male fireflies use specific light patterns to attract females and these displays are species-specific
– If a male of one species tries to attract the female of another, she would not be attracted to the strange light pattern and would not mate with the male
What is gametic isolation?
· It is like trying to fit a square peg in a circular hole.
· The reproductive organs of the insects and animals do not fit together, or do not fit together well.
· Or literally the sperm and the egg are incompatible, and do not come together even when they are right up next to each other. Failure to make zygote.
· “A gametic barrier exists when differences in gamete cells (eggs and sperm) prevent fertilization from taking place. Similarly, in some cases closely related organisms try to mate, but their reproductive structures simply do not fit together. Example: damselfly males of different species have differently shaped reproductive organs (below). If one species tries to mate with the female of another, their body parts simply do not fit together.”
Damselflies
Damselfly penile shapes
What is structural isolation?
· In plants, certain structures aimed to attract one type of pollinator simultaneously prevent a different pollinator from accessing the pollen. The tunnel through which an animal must access nectar can vary widely in length and diameter, which prevents the plant from being cross-pollinated with a different species. Some flowers have evolved to attract certain pollinators. The (a) wide foxglove flower is adapted for pollination by bees, while the (b) long, tube-shaped trumpet creeper flower is adapted for pollination by humming birds.
pollination