Std.9 Evolution ReviewExplain how comparing embryology, DNA, and homologous structures can help establish evolutionary relationships.

What is an isolating mechanism? How can it lead to the formation of a new species (speciation)

Define natural selection: ___________________________________________________________________________________

Matching: Relate each term to the process of evolution

_____Struggle for existence

_____Survival of the fittest

_____Fitness

_____Adaptation

a. Inheritable anatomical, behavioral, or physiological traits that increase an individual’s ability to survive.

b. Ability to survive and reproducec. Competition for food, space, and vital resourcesd. Process by which individuals who possess the best adaptations survive and reproduce

Natural variation in populations results from: ____________________________ & __________________________

The founder effect and the bottleneck effect are both examples of genetic ____________________ which is a (circle one)

random / specific change in allele frequency that affects (circle one) large /small populations.

Question Analysis

Which of these best illustrates natural selection?

a. An organism with favorable genetic variations will tend to survive and breed successfully.b. A population monopolizes all of the resources in its habitat, forcing other species to migrate.c. A community whose members work together utilizes all existing resources and migratory routes.d. The largest organisms in a species receive the only breeding opportunities.

A small portion of a population that is geographically isolated from the rest of the population runs the risk of decreased

a. genetic drift. c. natural selectionb. mutation rate. d. genetic variation

Explain:

A species of finch has been studied on one of the geographically isolated Galapagos Islands for many years. Since the island is small, the lineage of every bird for several generations is known. This allows a family tree of each bird to be developed. Some family groups have survived and others have died out. Why have some groups survived while others have not? Explain

A population of termites initially consists of darkly colored and brightly colored members. After several generations, the termite population consists almost entirely of darkly colored members because the brightly colored termites are easier for a predatory species of insectivores to locate. This situation is an example of what? Explain.

Fossil evidence suggests that a number of members of one fish species from an ancient lake in Death Valley, California, became several isolated species. Each of these new species lived in a different pond. Which of the following best explains the cause of this speciation?

a. episodic isolation c. geographic isolationb. temporal isolation d. behavioral isolation

Explain:

Earth has undergone some catastrophic changes from time to time. Which of these most likely explains why life on Earth continued following these catastrophes?

a. Dominant species had a slow mutation rate.b. Many species filled the same niche.c. A strong species had many different characteristics.d. A wide diversity of species existed.

Explain:

Std.9 Evolution Study GuideI. Evolution*Evolution → change in species over time; modern organisms descended from ancient organisms* natural variation exists in nature; each organism uniquely adapted to environment.*Charles Darwin = evolution by natural selection* Natural selection = mechanism of evolution → survival of the fittest.

Struggle for existence – competition for food, living space etc.

Survival of the fittest – individuals with best adaptations survive

Fitness – ability to survive and reproduce → best adaptations Adaptations → increases fitness

o Anatomical – physical → (strength/speed)o psychological – behavioral → (aggressiveness)o Functional – physical process → (photosynthesis)

*Descent with Modification - each species has descended, with changes, from other species over time.

II. Genetic Variation Gene pool – combined genetic info. of all members of a

populationo Member share common group & interbreed

* Natural selection acts on phenotype variation. Diversity sources: mutations – random change in DNA sequence gene shuffling – random recombination of genes (sexual

reproduction) increases variation.o Species diversity increase ability to survive

Single-gene traits – controlled by one gene (only 2 phenotypes)

Polygenic traits are controlled by two or more genes = many phenotypeso Directional selection – favors one extreme (end of curve)o Stabilizing selection – best adapted = middle of curveo Disruptive selection – selects against the middle

III. Genetic Drift* genetic drift – quick, random change in allele frequency caused by chance; reduces variation

Founder effect – small group separates, new small gene pool Bottleneck effect- sudden reduction in population; only a

small group survives – chance & quickly Natural disaster – reduces gene pool, reduces diversity &

variation

IV. Speciation * Speciation – changes leading to the formation of a new species.

Isolating Mechanismso Reproductive Isolation –cannot interbreed and produce

viable offspring (gametes incompatible)

o Behavioral –differences in courtship rituals or other types of behavior (i.e. birds singing)

o Geographic – 2 populations are separated by geographic barriers such as rivers or mountains

o Temporal – Two or more species reproduce at different

times .