History of Life on Earth
Chapter 12
The Age of the Earth
____________________________

Radiometric dating
–
Radioactive isotopes break down over time
–
____________________ – time it takes for half of amount to decay
–
Using this can estimate age of earth
–
Non-living chemicals reacted and produced organic molecules

Combination of chemicals and energy from lightning/heat/Sun’s UV created

____________________________
2 Theories about how

Primordial Soup
Oceans
filled with organic molecules
Sparks
simulate _______________
Amino
acids, fatty acids. And other hydrocarbons formed
1
problem: no _____________ to protect from _____, certain compounds
couldn’t have existed
Bubble Model
Gases
from ____________________________ trapped in bubbles that
protect them from UV and concentrate them
Reactions
Bubbles
Energy
happen faster
rise, burst, release compounds
from UV and lightning creates more reactions
____________________________
fall into ocean and start again
Precursor of 1st Cells
Molecules
_______
RNA
of life can arise from ____________________________
can be made in lab
believed to be 1st ____________________________storing molecule
Makes
proteins and changes from generation to generation; acts as an
enzyme
_______________
–____________________________form
droplets in water
_______________
–Droplet
made of different kinds of molecules like amino acids and
sugars
These
are steps toward cellular organization
Microspheres
last longer and longer and bring other molecules in
Origin of Heredity
_______
came after RNA
RNA
catalyzed early proteins
Many
believe RNA was brought into microsphere and could pass traits on
But
how DNA, RNA, and hereditary mechanisms first developed is still not
known
12.2 The Evolution of Cellular Life:
Prokaryotes
___________:
preserved or mineralized remains or imprints of an organism
that lived long ago
Oldest
(__________________________) photosynthetic prokaryotes -
___________________________
Created
oxygen but took millions of years to build up to current amount
Two Groups of Bacteria Split Very Early
_____________________
–__________________________
–Many
in cell walls
cause disease and decay
_____________________
–No
peptidoglycan
–Unique
lipids in cell membrane
–Believed
to resemble ancient archaebacteria
Evolution of Eukaryotes
_______________
Larger;
first eukaryotes showed up
__________________________; DNA in nucleus
–Mitochondria in almost all
–Chloroplasts in plants and protists
__________________________
Theory
states bacteria entered large cells as _____________ or
________________
Begin
to live inside host and performed cellular respiration or photosynthesis
Mitochondria
Chloroplasts
– descendents of symbiotic, ____________ eubacteria
– descendents of symbiotic, ________________ eubacteria
Support for Endosymbiosis
____________________________
–Mitochondria like eubacteria
–Chloroplasts like cyanobacteria
____________________________
–Circular DNA similar to bacteria is different than hosts DNA
____________________________
–Similar in size to those of bacteria
____________________________
–Simple fission independent of host
Multicellularity
All living things are broken into ____kingdoms

________________________________________________________
–
Eubacteria and Archaebacteria ____________; single celled prokaryotes

Protista – first _____________ kingdom, multicellular and unicellular

All other eukaryotes, fungi, plants, and animals, came later and all came

from _________________
Unicellular
Almost
is very successful
every cell you can see is multicellular
Origins of Modern Organisms
________________________________________________________
–Most
animal phyla originated during late _____________________ and
early _________________________ periods
–Great
evolutionary expansion
–Many
unusual marine organisms appear that have no living relatives
Burgess Shale
1909
geological formation in Canada found
Ordovician
Period – 505 mya – 438 mya
–______________ – extinct 250 mya
Burgess Shale
Mass Extinctions
Large
___
number of species become extinct
Major extinctions
–440
mya
–360
mya
–245
mya – _______________________________
–210
mya
mya – ________________________________
–65
Today?
–½
Human activity might be causing another
of rainforests destroyed
–Keep
up our current rate
22% to 47% of plants gone

2,000 of the 9,000 birds

12.3 Life Invaded Land
____________________________
–Life
evolved protected in oceans from dangerous UV rays from Sun
–No
life on land during Cambrian period
–2.5
bya photosynthesis puts O2 into air which reacts and forms Ozone,
O3
–Blocks
UV
Eventually enough to make it safe to live on land
–
Plants and Fungi on Land
1st
organisms on land were probably a combination of plants and fungi; 430
mya
–Plants
can make nutrients by photosynthesis
–Fungi
can absorb minerals from rock
–Together
called _______________________, these exist today
_______________________
– 2 species live together and both benefit