Chapter 4

Question 1

What is a species?

Answer 1

-a group of interbreeding organisms that is reproductively isolated from other organisms.

Question 2

How do species evolve?

Answer 2

-Microevolution- evolution within a species.
Relatively easy to student in the field or lab

Macro evolution- Takes longer, difficult to observe in a lifetime.

3 ways of looking at speciation
1 Allopatric- has to be a physical barrier between population
- selection may favor different phenotypes in these isolated populations.
Eventually result in speciation.
- interbreed.
Allopatric Speciation:
1)Character Displacement- despite gene flow, the 2 populations may evolve into 2 distinct species.
2) Reinforcement- selection will favor behavioral and morphological adaptations that increase mating success.
- Reinforcement appears as different courtship behaviors or mating songs , leading to reproductive isolation.

2 Parapatric Speciation- Example African baboons.
Weaker version
Different species have evolved in each habitat.
Hybrid zones = baboons interbreed. Better to adapt. Learn hybrid for parapatric.
If hybrids become more fit, reinforcement causes baboons to become reproductively isolated.

3 Sympatric Speciation- the stronger version
Natural selection creates different phenotypes and species.

Parapatric and sympatric Speciation:
May favor 2 adaptations to the same environmental problem.
May result in the evolution of 2 different species.

Question 3

How do researchers reconstruct the Tree of Life?

Answer 3

The Tree of Life
• Connected through a common
ancestry
• We share the same structures,
homologies
• Example: Forelimb (as seen in
the images)
• Natural selection has modified these
bones to produce morphologies best
fit for the environment in question 

Phylogenetic reconstruction allows
researchers to examine why certain
species evolved certain adaptations, and
not others
Example: great apes all move in slightly
different ways

Question 4

Why do we care which species are most closely related to humans?

Answer 4

To learn more about humans evolution, characteristics, and where they derived from.their common ancestors.

Question 5

What is phylogenetics? What is taxonomy?

Answer 5

• Phylogenetics is the study of the evolutionary history and relationship among individuals or group of organisms.
• Taxonomy is a branch of biology that is concerned with the use of phylogenies for naming and classifying organisms.

Question 6

Microevolution

Answer 6

-Evolution of populations within a species.

Question 7

Macroevolution

Answer 7

-Evolution of new species, families and higher taxa.

Question 8

Species

Answer 8

-A group of organisms classified together at the lowest level of the taxonomic hierarchy.

Question 9

Biological species concept

Answer 9

-The concept that species are defined as a group of organisms that cannot interbreed in nature. Adherents of the biological species concept believe that the resulting lack of gene flow is necessary to maintain differences between closely related species.

Question 10

Reproductive isolation

Answer 10

-A relationship between two populations in which there is no gene flow between them.

Question 11

Gene flow

Answer 11

-The movement of genes from one population to another, or from one part of a population to another, as a result of interbreeding.

Question 12

Ecological species concept

Answer 12

-The concept that natural selection plays an important role in maintaining the differences between species, and that the absence of interbreeding between two populations is not a necessary condition for defining them as a separate species.

Question 13

Allopatric speciation

Answer 13

-Speciation that occurs when two or more populations of a single species are geographically isolated from each other and then diverge to form two or more new species.

Question 14

Character displacement

Answer 14

-The result of competition between two species that causes the members of different species to become morphologically or behaviorally more different from each other.

Question 15

Reinforcement

Answer 15

-The process in which selection acts against the likelihood of hybrids occurring between members of two phenotypically distinctive populations, leading to the evolution of mechanisms that prevent interbreeding.

Question 16

Parapatric speciation

Answer 16

-a 2 step process of speciation in which
1 selection causes the differentiation of geographically separate, partially isolated populations of a species.
2 subsequently the populations become reproductively isolated as a result of Reinforcement.

Question 17

Hybrid zone

Answer 17

-a geographic region where 2or more populations of the same species or 2 different species overlap and interbreed. They usually occur at the habitat margins of the respective populations.

Question 18

Sympatric speciation

Answer 18

-A hypothesis that speciation can result from selective pressures favoring different phenotypes within a population, without positing geographic isolation as a factor.

Question 19

Niche

Answer 19

-The way of life or “trade” of a particular species- what foods it eats or how the food is acquired.

Question 20

Adaptive radiation

Answer 20

-the process in which a single lineage diversifies into a number of species, each characterized by distinctive adaptations. The diversification of mammals at the beginning of the Cenozoic era is an example of adaptive radiation.

Question 21

Phylogeny

Answer 21

-the evolutionary relationships among a group of species, usually diagrammed as a “ family tree”

Question 22

Hominoids

Answer 22

-any member of the superfamily Hominoidea, which includes humans, all the living apes, and numerous extinct ape like and human like species from the Miocene, Pliocene, and Pleistocene epochs.

Question 23

Taxonomy

Answer 23

-a branch of biology that is concerned with the use of phylogenies for naming and classifying organisms.

Question 24

Quadrupedal

Answer 24

-describing locomotion in which the animal moves on all 4 limbs.

Question 25

Knuckle walking

Answer 25

-a form of quadrupedal locomotion in which, in the forelimbs, weight is supported by the knuckles, rather than by the palm or outstretched fingers. Chimpanzees and gorillas are knuckle walkers.

Question 26

Comparative method

Answer 26

• a method for establishing the function of a phenotypic trait by comparing different species.

Question 27

Terrestrial

Answer 27

-active predominantly on the ground.

Question 28

Arboreal

Answer 28

-active predominantly in trees.

Question 29

Systemics

Answer 29

-a branch of biology that is concerned with the procedures for constructing phylogenies.

Question 30

Analogous

Answer 30

-Similarity between traits that is due to convergent evolution, not common descent . For example, the fact that humans and kangaroos are both bipedal in an analogy.

Question 31

Homologous

Answer 31

-similarity between traits that is due to common ancestry, not convergence. For example, the reason that gorillas and baboons are both quadrupedal is that they are both descended from a quadrupedal ancestor.

Question 32

Ancestral trait

Answer 32

-a trait that appears earlier in the evolution of a lineage or clade.
Ancestral traits are contrasted with derived traits, which appear later in the evolution of a lineage or clade.
For example, the presence of a tail is ancestral in the primate lineage, and the absence of a tail is derived.
Systematists must avoid using ancestral similarities when constructing phylogenies.

Question 33

Derived trait

Answer 33

-A trait that appears later in the evolution of a lineage or clade. Derived traits are contrasted with ancestral traits, which appear earlier in the evolution of a lineage or clade.
For example, the presence of a tail is ancestral in the primate lineage, and the absence of a tail is derived.
Systematists seek to use derived similarities when constructing phylogenies.

Question 34

Out-groups

Answer 34

-a taxonomic group that is related to a group of interest and can be used to determine which traits are ancestral and which are derived.

Question 35

Genetic distance

Answer 35

-A measure of the overall genetic similarity of individuals or a species. The best estimates of genetic distance utilize large numbers of genes.

Question 36

Molecular clock

Answer 36

-The hypothesis that genetic change occurs at a constant rate and thus can be used to measure the time elapsed since two species shared a common ancestor. The molecular clock is based on observed regularities in the rate of genetic change along different phylogenetic lines.

Question 37

Neutral theory

Answer 37

-a theory postulating that genetic change is caused by mutation and drift.

Question 38

Genus

Answer 38

-a taxonomic category below family and above species. There maybe several species in a genus, and several genera in a family.

Question 39

Family

Answer 39

-a taxonomic level above genus but below order. A family may contain several genera, and an order may contain several families. Human beings belong to the family Hominidae, and the other great apes belong to the family Pongidae.

Question 40

Superfamily

Answer 40

-the taxonomic level that lies between infraorder and family. An infraorder may contain several super families , and a superfamily may contain several families. For example humans are a member of the superfamily Hominoidea , which contains the families Hominidae and Pongidae.

Question 41

Cladistic taxonomy

Answer 41

-a system for classifying organisms in which patterns of descent are the only criteria used.

Question 42

Evolutionary taxonomy

Answer 42

-a system for classifying organisms that uses both patterns of descent and patterns of overall similarity.