Evolution and Natural Selection

Across
3.	The process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time
4.	The preserved remains of plants/animals whose bodies are buried in sediment, such as sand or mud, under ancient seas, lakes and rivers
6.	A heritable trait that increases an individuals fitness
7.	The process by which traits that improve an organism’s chances for survival and reproduction are passed on more frequently to future generations than those that do not
9.	A change in a population’s gene pool over time
13.	A feature that a species inherited from an ancestor but that is now less elaborate and functional than in the ancestor
14.	How reproductively successful an organism is in its environment
16.	A physical incompatibility between reproductive organs of two organisms
17.	Biological evolution that occurs by chance
18.	The disappearance of a species from Earth
19.	Similar physical features in organisms that share a common ancestor, but the features serve completely different functions

Down
1.	When two populations differ in their periods of activities or reproductive cycles
2.	The process by which new species are generated
3.	A sequence of DNA that codes for a particular trait
5.	The idea that organisms best adjusted to their environment are the most successful in surviving and reproducing
6.	The process of selection conducted under human direction
8.	The separation of groups of organisms as a result of changes in their ecology or in the environment in which they live
10.	The physical separation of members of a population
11.	Features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature
12.	Changes in DNA
15.	When mismatches in mating traits prevent mating between two species/populations