Intro to Life Processes - Chapter 23

Human Evolution

Existence Hypothesis

• best hypothesis that suggests that life first evolved on Earth between 3.5 and 4 billion years ago

• life likely evolved from non-living matter in 4 stages (small organic molecules, polymers, protocell, cell)

• earths early atmosphere was much hotter and significantly different (water, nitrogen, carbon dioxide, hydrogen, carbon monoxide)

Thermal Vent Hypothesis

• Hydrothermal vents at the bottom of the ocean emit:

  • carbon monoxide

  • ammonia

  • hydrogen sulfide

• gases pass over iron and nickel sulfide (catalysts) to create organic molecules

Seeded Earth Hypothesis

• asteroids and meteorites have been confirmed to contain some organic molecules

  • as they crashed to earth, they may have seeded Earth with the organic compounds necessary for life to evolve

Panspermia Hypothesis

life evolved somewhere other than Earth, and bacteria-like protists were carried to earth by a comet or meteorite

• in 2015, the Churyumov-Gerasimenko comet was found to have glycerin and phosphorus in it

• Glycerin is typically found in fat, and phosphorus is essential for ATP and DNA

Prokaryotic

• first cells to exists

• no nucleus

• no membrane-bound organelles

• single-celled organisms

• the first eukaryotic cells were single-celled protists; protists eventually evolved into plants, animals, and fungi

Natural Selection

• proposed mechanism of biological evolution (Darwin and Walace called this “Decent with modification”)

• requires:

  • variation

  • competition for limited resources

Adaptation

a characteristic that gives an advantage in survival and/or reproduction to those organisms that have it

Lamarckian Evolution

species change by the inheritance or acquired characters

Fossil Record

• evidence of evolution

• remains of organisms from 10,000 to billions of years ago, which shows the record of how species changed over time, and documents some intermediate species

Biogeography

• evidence of evolution

• the study of the distribution of organisms throughout the world

• shows patterns of groups of organisms living in specific places, as they descended from common ancestors

Homologous Structures

structures that are anatomically similar between species because of shared ancestry

Vestigial structures

features that are fully developed in one related group of organisms, but which are reduced and may have no function in another related group of organisms

Biochemical Evidence of Evolution

Almost all living organisms use:

• DNA

• ATP

• The same (or nearly the same) enzymes

• the same neurotransmitters (serotonin, ACH, GABA)

Binomial names

taxonomic designation used to differentiate different types of organisms by using their designated genus and species name

• human genus species is homo sapiens

Primates

placental mammals adapted for living in trees, which have mobile limbs, grasping hands, a flattened face, binocular vision, a large, complex brain, and a reduced reproductive rate

Prosimians

group that includes lemurs, tarsiers, and lorises

Anthropoids

monkeys, apes, and humans (redundant because humans are technically apes)

Large Complex Brain

• the evolutionary trend among primates is generally towards large and more complex brains

• smaller section of the brain devoted to the sense of smell

• larger portion of the brain devoted to sight, and the control and processing of the hands (especially the thumb)

• Results in better eye-hand coordination

Human Spine and Anatomy

• in humans, the spine exists inferior to the center of the skull, and this places the spine at the midline of the body

• the longer, S-shaped spine of humans places the trunk’s center of gravity directly over the feet

• the broader pelvis and hip joint of the humans keep them from swaying when they walk

• longer femur in humans caused the femur to angle inward at the knees (modified to support the full human weight)

• human toe is not opposable; arched foot allows for long distance walking/running with less change of injury

Evolutionary tree

represents a working hypothesis of evolutionary history based on the characteristics of each group of organisms

Hominids

humans, chimps, gorillas, and orangutans

Hominins

• humans and other now extinct human-like species

• Bipedal posture - walking on two feet

• Shape of the face - flatter face with a shorter jaw

• Teeth - smaller and less specialized than other great apes

• Brain size - modern humans ~13600 cc; chimp ~400 cc

Cro-Magnons

the oldest fossils to be designated Homo sapiens, named from the location they were found in France

• entered Asia and Europe from Africa before 100,000 years ago

• had a modern appearance

• had distinct DNA from H. neanderthalensis indicating that the two groups did not initially interbreed

• H sapiens and H neanderthalensis apparently interbred in Europe ~40,000 years ago

• made advanced, compound tools with wooden handles

• they may have been the first species to use ranged hunting weapons

• during the Pleistocene epoch they have been implicated in the extinction of the giant sloth, mammoth, sabertoothed tiger, and the giant ox

• made a variety of forms of art

Lecture 8 Evolution of Hominins

look at slides for ethnicities, skin tones, etc (at the end of 23.4)