History Of Life

K-T Boundry

Line of clay with high levels of iridium (space rock) dating back to the extinction of dinos

Asteroid Impact Hypothesis

debris blocked sun, photosynthetic processes stopped, plant eaters dies, meat eaters dies, end of Mesozoic Era

Evidence for Asteroid Hypothesis

spherules (glass-like beads) + shocked quartz

First Signs of Life After Asteroid Were….

FERNS!!! and smaller burrowing mammals

How much of life was wiped out following impact?

¾ plant, animal species

How can radiometric dating be used to determine the age of fossils?

the ratio of elements in the sediment can tell the age of fossils in the rock

Why is radio carbon dating not used after 1950s?

atomic bomb testing messed with C-14 levels in atmosphere

Plate tectonics theory

earth’s outer mechanical layer is made of constantly moving plates

Convergent Plates

Move toward each other

Transformation Plates

Move against each other

Divergent Plates

Move away from each other

Extinctions

death of life forms called species

Adaptive Radiations

After extinction survivors undergo successful flourishing to fill vacant niches

Mass Extinction Examples

Permian-Triassic (90% species go extinct, end of reptile domination, origin and radiation of dinos, origin of mammals) and Cretaceous-Tertiary (end of dino, mammal radiation)

Permian Triassic Extinction

250 million years ago, 90% species extinction, Trilobites Extinct, dinos the dominant vertebrate

Cretaceous-Tertiary Extinction

65 million years ago, 75% species extinction, begin mammal domination

Pedomorphosis

retention of juvenile features into adulthood

Homeotic Genes

control form

Difference of Hox Expression

early- arm bones, later- wrist and digits

How did the Stickleback fish evolve?

loss pelvis spine (body armor) in freshwater which is the equivalent of loss of hind legs

PitX1 Gene in Stickleback

gene switch deleted NOT the gene