1. Hominid Evolution

2. Hominid Evolution
• Hominids family of organism
that includes humans
• First appeared between 6 and 7
million ears ago
• Has evolved several times..we can
tell by looking at fossil
evidence…Skulls in particular

3. Hominid Evolution
• Today researchers believe Hominid
evolution proceed by
• Adaptive radiation is a process by
which a several species evolve from
single ancestral species.

4. Hominid Evolution
• Adaptations in hominid
evolution include …
• Bipedal locomotion-walking
upright on 2 legs
• Large brains- specially
cerebrum; Increase in cranial
capacity
• Changes in skull shape,
including decrease in size of
brow ridge (section of bone
above eye)
• Decrease in jaw size and
angle at which jaw
protrudes from face
• Decrease in the number of
teeth
• Opposable thumbs- adapted
for grasping

6. • Homo habilis-
– Oldest…existed 2 million years ago
– handy man.” fossils found with tools
• Homo erectus means upright human
– Existed 1.6 million years ago to about 200,000 years ago
– Taller and larger brain than Homo habilis
– Smaller teeth than Homo habilis
– Lived in groups (suggest language use) and used fire
• Homo sapiens- means wise human
– Existed about 100,000 to 200,000 years ago
– Some believe they arose directly from Homo erectus while
other believe they arose from Homo Neanderthals (who
descended from Homo erectus)
– By about 40,000 years ago, H. sapiens were physically
identical to modern humans
• Homo neanderthalensis - Neanderthals
– Emerged in Germany 300,000 years ago
– Lived till about 30,000 years ago
– made stone tools and lived in organized social
groups and had organized societies
– Brain was similar in size to modern humans
– DNA evidence now supports this theory…modern
human DNA is 99.7 % identical to that of the
Neanderthals

8. Embryology Zygote formation
Cleavage
4 cells
• Zygote
– When male gamete fertilizes female gamete Morula
– Gametes fuse, making one new cell with
chromosomes from both parents Blastocyst
– Zygote will divide into 2 new cells…each of
those into 4 and so on…
– Cleavage  division of embryonic cells to
form two new cells
• Genetic material is copied before each cleavage
• Blastula
– Hollow ball of cells
• Gastrula
– When blastula implants itself on the uterine
wall (to get nourishment from mother)
– Ball of cells composed of three layers “GERM
LAYERS” (undifferentiated)

10. Gastrula
• Germ layers
– Differentiation
the process by
which a cell
develops in
different ways to
perform different
functions…begins
with the forming of
three germ layers
– Ectoderm
• Outer layer
• Forms skin, nerves
and sense organs
– Mesoderm
• Middle layer
• Forms bones, muscles
and connective tissue
– Endoderm

11. Fetus
• When the structures of the
developing embryo have
become distinguished
• Cells have differentiated into
their permanent role in that
organism