Great transitions the origin of tetrapods Tiktaalik 17

Great transitions: the origin of tetrapods (Tiktaalik) (17 min): https: //www. biointeractive. org/classroomresources/great-transitions-origin-tetrapods Great transitions: the origin of birds (18 min) https: //www. biointeractive. org/classroomresources/great-transitions-origin-birds The day the Mesozoic died (33 min): https: //www. biointeractive. org/classroomresources/day-mesozoic-died

4 Modes of Natural Selection

Directional Selection: Quantitative or polygenic traits:

Directional Selection:

Directional Selection: Drosophila : flying to and away from light.

Directional Selection: Hunting has reduced horn size in bighorn sheep.

Size of horns (units) Change in size of horns of bighorn sheep rams in Arizona.

Directional Selection: Seed-size and beak size in Galapagos finches.

Beak depth of Galapagos finches: environment heterogeneous in time.

Directional Selection: Speed of horse running.

Stabilizing Selection:

Stabilizing Selection: birth weight.

Stabilizing Selection: Body mass.

Disruptive Selection:

Disruptive Selection: Drosophila.

Disruptive Selection: African swallowtail (Papilio dardanus).

Sexual Selection:

Sexual Selection: (a) intra-sexual: fight-the-same. (b) Inter-sexual: charm-the-other.

Natural Selection leads to: In a stable environment:

However,