A major purpose of our course is to interpret variations in plants that occurs at various levels (e.g., individuals to species). We will learn how to identify it, and will speculate about why it's there.

Biologists assign organisms to classification schemes that reflect their overall similarity and difference (i.e. a reflection of genetic (evolutionary) relatedness)

We have already been introduced to some types of variation in first lab: Angiosperms vs. Gymnosperms

Let's focus on the levels of variation within species and between closely related species (Fill in the sources of variation).

GENOTYPE X ENVIRONMENT = PHENOTYPE

Traits (e.g., leaf size, shape) reflect ways that environment modifies expression of genetic make up.

DNA (genetic code) contains information for traits. Provides continuity between generations of cells (organisms)-replicated when cells divide:

mitosis (cell division in growth)
meiosis (cell division in reproduction that produces egg and sperm cells)

Genes are expressed in different ways (some dominant, some not). Expression is also modified by environment (high light intensity results in thick leaves with waxy covering).

Thus genotype (genetic make up) can be modified by environment so that phenotype (appearance or performance) differs in different environments.

Over long time scales environment modifies composition of genetic code by allowing certain genotypes to prevail (i.e. the process of natural selection, evolution).

Common gardens: general term for planting trees in same place (environment)-differences must be due to genetic differences

Provenance test: type of common garden test that assesses genetic differences related to geographic location (i.e., geographic races).