A 3.1 Diversity of organisms

Why is variation essential for evolution?

It provides differences for natural selection to act on.

At what levels does variation occur?

Between species, between individuals, and within individual traits.

Why is variation a defining feature of life?

It enables adaptation and evolutionary change.

What is the morphological species concept?

Classifying species based on physical appearance.

What is the biological species concept?

Species can interbreed and produce fertile offspring.

Why are lions and tigers an exception to the biological species concept?

They can interbreed and produce fertile offspring despite being different species.

What is the difference between fertile and infertile offspring?

Fertile offspring can reproduce; infertile offspring cannot.

How is the genus written?

Italicized, first letter capitalized.

How is the species name written?

Italicized, all lowercase.

How do you abbreviate a species name after first use?

Shorten the genus to its first letter (e.g., L. argentatus).

What is a population?

Same species, same area, same time.

What causes speciation to begin?

Geographic isolation that stops interbreeding.

Why is speciation hard to define precisely?

It is a slow, gradual genetic divergence.

Why is chromosome number important in species?

It is a consistent characteristic that can change through fusion or splitting.

What is a karyogram?

A photo of chromosomes arranged by size and centromere position.

Give chromosome numbers for humans, chimps, and platypus.

Humans 46; chimps 48; platypus 52.

What genetic feature is shared within a species?

Same genes in the same order on chromosomes.

What are SNPs?

Single base differences that create genetic diversity.

Does genome size correlate with complexity?

No — larger genomes don’t mean more complex organisms.

What is junk DNA?

DNA with no known function (about half of human DNA).