Ap Bio Chapter 22, 23, & 24

Front 1

What is speciation?

Back 1

Speciation is the process where one species splits into 2 or more species. It creates diversity and explains why many species share features.

Speciation is the bridge between microevolution and macroevolution.

Front 2

What is microevolution?

Back 2

(changes in allele frequency in a population)

Front 3

What is macroevolution?

Back 3

(evolution at the species level)

Front 4

What is the biological species concept?

Back 4

The biological species concept states a species is a group of populations whose members have the ability to interbreed in nature and produce viable, fertile offspring (but don’t produce viable, fertile offspring with members of other groups).

Front 5

reproductive isolation

Back 5

Reproductive isolation consists of biological barriers that prevent two species from interbreeding and producing viable, fertile offspring.

Front 6

Barriers blocking gene flow

Back 6

Barriers block gene flow between and reduce the formation of hybrids (offspring that results from the mating of two different species). Sometimes it takes more than one barrier to isolate a species’ gene pool.

Front 7

2 Types of Barriers

Back 7

-Prezygotic and Postzygotic

There are two separate types of barriers based on isolation before or after fertilization. Prezygotic (before the zygote) barriers block fertilization and postzygotic (after zygote) barriers contribute to reproductive isolation after the hybrid is formed.

Front 8

Prezygotic barriers:

Back 8

-Habitat isolation- Two species occupy different different habitats in the same area but rarely encounter one another (water fowl and birds on land).

-Temporal isolation- The species breed at different times of the day, seasons, or years preventing reproduction (Eastern spotted skunk breeds in late winter and western spotted skunk breeds in late summer).

-Behavioral isolation- Courtship rituals that attract mates of the same species (male blue-footed boobie high stepping to show his blue feet to a potential mate).

-Mechanical isolation- mating is attempted but difference prevent successful completion (the shells of two species of snails spiral in different directions preventing their genitals from aligning properly).

Front 9

What are some other definitions of species?

Back 9

The morphological species concept characterizes a species by their body shape/structure. The issue with using this distinction is trying to agree on which structures distinguish a species.

The ecological species concept looks at a species based on its ecological niche (how the members of the species interact with the living and nonliving parts of their environment).

The phylogenic species concept defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.

Front 10

Discuss speciation with or without geographic separation.
W/ Allopatric (other country) and Sympatric (same country)

Back 10

Allopatric (other country) speciation occurs when gene flow is interrupted when a population is split into geographically isolated sub populations (river changes course and divers two populations or the water levels in a lake decreases creating two smaller lakes with separate populations).

The separation can cause gene pools to diverge. Different mutations, natural selection, and genetic drift can change the allele frequency in the two populations. Reproductive isolation can then arise from the genetic divergence Ex. Mosquito fish p. 423

Sympatric (same country) speciation occurs in populations that live in the same geographic area (it isn’t as common as allopatric speciation).

Sympatric speciation can occur if gene flow is reduced by polyploidy, habitat differentiation, and sexual selection.

Front 11

Habitate differentiation
when does it occur?

Back 11

-Habitate differentiation occurs when genetic factors let a subpopulation exploit a habitat or resource not used by the parent population. The North aAmerican Apple maggot fly is an example. The fly’s original habitat was the Hawthron tree, but 200 years ago some populations colonized apple tree planted by European settlers. Apples mature faster then hawthorn fruit, and though natural selecetion the apple feeding flies develop faster. The apple feeding flies now have temporal istolation (breeding times) from the hawthrown feeding flies.

Front 12

Sexual selection
when does it occur?

Back 12

-Sexual selection typically occurs when females select mates based on appearance and is thought to be a possible answer to the number of cichlids species produced in East Africa’s Lake Victoria (up to 600 species from a few colonizing species). See figure 22.2

Front 13

What is Polyploidy and when does it occur?

Back 13

Polyploidy occurs when an accident happens during cell division giving one cell too many chromosomes. It is not common in animals (the grey tree frog is thought to originate this way) but happens more frequently in plants.

Front 14

Two types of polyploidy

Back 14

autopolyploidy and allopolyploidy

Front 15

Autopolyploidy

Back 15

An autoplolyploidy is an individual that has two chromosome sets dervived from a single species.

An example would be a plant cell that has double the number of chromosomes because cell division didn’t occur (cell no longer diploid [2n] but tetraploid[4n]). A tetraploid can produce fertile tetraploid offspring through self pollination or mating with other tetraploid plants but are now reproductively isolated from diploid plants.

Front 16

Allopolyploidy

Back 16

An allopolyploidy is a fertile polyploidy hybrid that can only mate with others like itself but not with either parent species that created it. (Remember, hybrids are created when two different species mate, but most are sterile. Some infertile hybrid plants can propagate asexually and after many generations change from a sterile hybrid into a fertile polyploidy).

Allopolyploidy is very rare but has created at least 5 plant species in the last 150+ years.

-Habitate differentiation occurs when genetic factors let a subpopulation exploit a habitat or resource not used by the parent population. The North aAmerican Apple maggot fly is an example. The fly’s original habitat was the Hawthron tree, but 200 years ago some populations colonized apple tree planted by European settlers. Apples mature faster then hawthorn fruit, and though natural selecetion the apple feeding flies develop faster. The apple feeding flies now have temporal istolation (breeding times) from the hawthrown feeding flies.

-Sexual selection typically occurs when females select mates based on appearance and is thought to be a possible answer to the number of cichlids species produced in East Africa’s Lake Victoria (up to 600 species from a few colonizing species). See figure 22.2

Front 17

What are hybrid zones?

Back 17

Hybrid zones are regions where members of different species meet and mate, producing some offspring of mixed ancestry. They occur where the habitats of the interbreeding species meet. This is seen when the habitats of the yellow-bellied toads (livein higher altitudes) and red bellied toads (live in lower altitudes) meet. The toads do meet and reproduce in a hybrid zone, but the offspring have poor survival and reproductive survival rates dues to embryonic and morphological anomalies (abnormal tadpole mouthparts and ribs fused to the spine).

Front 18

Overtime there are three outcomes for hybrid zones:

Back 18

-Rienforcement of barriers- Less fit hybrids and natural selection strengthens Prezyotic barriers and reduce the formation of unfit hybrids.

-Fusion of species- Two hybrid species fuse into a single species (reverse speciation).

-Stability- Hybrid zones become stable, continuing to produce hybrid organisms.

Front 19

What is punctuated equilibrium?

Back 19

Punctuated equilibrium involves periods time in the fossil records where no new species appear punctuated by times when many new species appear, then become extinct.

Some species don’t show punctuated, but gradual changes over time.

Front 20

Where are the richest sources of fossils found?

Back 20

The sedimentary rock layers (strata) have the greatest number of fossils.

The fossils give us a detailed account of biological changes that have occurred over time, but it is still an incomplete record (fossils destroyed by geological changes, organisms that existed but didn’t form fossils, or fossils that still remain undiscovered).

Fossils and rocks can be dated using radiometric dating (the decay of radioactive isotopes). The rate of decay of the isotopes is based on the time it takes for ½ of the parent isotope to decay, the half-life. This time to decay is stable and unaffected by temperature or pressure. Carbon-14 decays quickly with a half-life of 5730 years, whereas uranium 238 decays slowly with a half-life of 4.5 billion years.

Front 21

How was the geologic record created?

Back 21

The study of fossils lead to the creation of the geologic record. The geologic record divides the Earth’s history into four eons (Hadean, Archaean, Proterosoic, and Phanerozic), and eons are subdivided into eras.

The Phanerozic eon is divided into the Paleozoic, Mesozoic, and Cenozoic eras (each ear is then divided into periods). See p.439

Front 22

Discuss plate tectonics.

Back 22

The theory of plate tectonics explains the movement of continents over time (Pangaea).

The continents are part of plates of the Earth’s crust and float on the hot, underlying portions of the mantle. Convection causes the plates to move in a process known as continental drift. The plates move a few centimeters each year.

The continents drift affects life on Earth by altering habitats over long periods of time, affecting climate over long periods of time, and creating large scale allopatric speciation.

Front 23

Discuss mass extinction.

Back 23

Mass extinction occurs when large numbers of species become extinct. The fossil record shows that most of the species that have ever lived have become extinct.

Five mass extinctions have occurred during the last 500 million years. The Permian and Cretaceous extinctions are the most well known of the five.

Front 24

The Permian extinction

Back 24

The Permian extinction marks the boundary between the Paleozoic and Mesozoic eras (251 million years ago) and claimed roughly 96% of marine animals. Major volcanic eruption occurred during this time creating layers of lava hundreds to thousands of feet thick. High amounts of carbon dioxide raised the Earth’s temperatures, lower oxygen levels in the oceans, and affected the ozone layer.

Front 25

The Cretaceous extinction

Back 25

The Cretaceous extinction occurred 65.5 million years ago and marks the boundary between Mesozoic and Cenozoic eras. This is when the dinosaurs become extinct, possibly by an asteroid.

Front 26

The consequences of mass extinctions are as follows:

Back 26

-Loss of an evolutionary lineage (once an organism becomes extinct, evolution is changed forever)
-Altering ecological communities by changing the types of organisms

Front 27

Discuss adaptive radiation.

Back 27

Adaptive radiation constitutes periods of evolutionary change where groups of organisms form new species whose adaptations left them fill different riches in their community.


After each of the 5 mass extinctions surviving organisms became adapted to new riches ushering in large scale adaptive radiation.

After the extinction of the dinosaurs, mammals changed due to adaptive radiation.

Regional adaptive radiation is also seen in areas like the Hawaiian archipelago. The islands were formed from volcantic eruption and were there “nacked”. Organisms slowly inhabited the islands (traveling by way of wind and weather), with each islands displaying its own diversity.

Front 28

Discuss heterochrony.

Back 28

Heterochrony are evolutionary changes in the rate of timing of developmental events.

An organism’s shape is affected by the growth rates of different body parts during its development. If you change the rates of development, you alter the adult organisms form.

Heterochrony can also affect the timing of reproductive development. If sexual organs develop at a faster rate than normal, the organisms may retain juvenile structures even though they have become sexually mature (salamander that still retains gills and larval structures but are sexually mature). This is known as paedomorphosis (retention in an adult organism of juvenile features found in its evolutionary ancestors).

Front 29

Discuss evolutionary changes based on spatial patterns.

Back 29

Evolutionary changes can result form alterations in genes that affect the placement (special organization) of body parts. Where an organism’s limbs or wings, or where a plant’s flowers are placed is affected by regulatory genes (know as homeotic genes). One of these genes, the Hox gene, affect where many different embryonic organisms’ appendages are located.

Front 30

Discuss prokaryotes.

Back 30

Prokaryotic organisms (bacteria and archaea) were the first forms of life on Earth, and are cells lacking a nucleus or membrane bound organelles.

The oldest known prokaryotic organisms are approximately 3.5 billion years old cells:

-The abiotic synthesis of small organic molecules like amino acids and nitrogenous bases.

-These small molecules form protocells (droplets with a membrane and internal chemistry).