Traveling Efficiency Hypothesis -- more efficient to move from areas of scattered trees on the savannah -- saved energy to walk on two legs instead of four -- four legs gave speed but two legs were energy efficient

Postural Feeding Hypothesis -- increased ability to grab fruits hanging from trees

Provisioning Model -- could collect resources and take them back

Thermoregulatory Model -- reduced surface area exposed to the sun

Carrying Model -- freed up hands to carry food, tools, infants, to hunt, and to communicate

-- extinct lineage

-- earliest gnathostomes

-- armored vertebrates

-- name means “plate-skinned”

-- most were less than a meter long

-- some were more than 10 meters long

-- diverged 420 million years ago

-- diverged into      -- chrondrichthyes      -- ray-finned fishes      -- lobe-fins

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Cambrian Explosion -- relatively brief time in geologic history -- many present-day animal phyla appeared in the fossil record -- 535 to 525 million years ago

Bilaterians -- members of a clade of animals with bilateral symmetry and three germ layers

Ediacaran Biota -- early group of macroscopic, soft-bodied, multicellular eukaryotes -- found in fossils dated 635 to 541 million years ago

Valeria -- 800 million years ago -- roughly spherical -- no structural defenses -- soft-bodied

Spiny Acritarch -- 575 million years ago -- five times larger than Valeria -- covered in hard spines

Pikaia -- eel-like cordate

Anomalocaris -- large animal -- grasping limbs -- circular mouth

Hallucigenia -- animal with toothpick-like spines

-- lived in Eastern Africa      -- Turkana basin      -- southern Ethiopia

-- lived about 2.7 to 2.3 million years ago

-- very few remains have been found

-- earliest known robust australopithecine

-- had a strongly protruding face

-- had large megadont teeth

-- had a powerful jaw

-- had a well-developed sagittal crest on top of the skull

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