1 A BRIEF HISTORY OF LIFE ON EARTH Objectives • Describe how Earth’s environment has changed over the past 4 billion years. • Identify the minimum requirements for life. • Describe the difference between prokaryotic and eukaryotic organisms. • Define the theory of natural selection and how evolution works. • Describe several ways in which fossils form. • Describe the dramatic change in Earth’s biota during the Cambrian Period. The Ever- Changing Earth • Changes in the atmosphere and hydrosphere – Early atm. had no O 2 – Oldest bacteria: 3.5 by – Blue-green algae-2.5by, – Photosynthesis – Banded iron formation 2.5-1.8 by
9
Embed
A BRIEF HISTORY OF LIFE ON EARTH - Homepages at …homepages.wmich.edu/~kehew/Geos1000/ch14_earth_hisotry.pdf1 A BRIEF HISTORY OF LIFE ON EARTH Objectives •Describe how Earth’s
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
A BRIEF HISTORY OF LIFE
ON EARTH
Objectives
• Describe how Earth’s environment has changed over
the past 4 billion years.
• Identify the minimum requirements for life.
• Describe the difference between prokaryotic and
eukaryotic organisms.
• Define the theory of natural selection and how
evolution works.
• Describe several ways in which fossils form.
• Describe the dramatic change in Earth’s biota during
the Cambrian Period.
The Ever-
Changing Earth• Changes in the
atmosphere and
hydrosphere
– Early atm. had no O2
– Oldest bacteria: 3.5 by
– Blue-green algae-2.5by,
– Photosynthesis
– Banded iron formation
2.5-1.8 by
2
The Ever-Changing Earth• Photosynthesis
– A chemical reaction
whereby plants use light
energy to induce carbon
dioxide to react with water,
producing carbohydrates
and oxygen
• Oxygen content increases
in the atmosphere
Banded iron formations
formed during the transition to
more oxygen rich atm.
Cyanobacteria (algae)
produced the oxygen initially.
They formed the first fossils,
which were mounds of
calcium carbonate
(stromatolites)
The Ever-Changing Earth
3
Oxygen content in the atmosphere increased starting
around 200 my. The deposition of large amounts of
organic matter on shallow marine shelves due to plate
tectonics may have allowed this increase.
Early Life
• Archean and proterozoic
life
– Prokaryote• A single celled organism with
no distinct nucleus… or, no
membrane separates its DNA
from the rest of the cell- all
bacteria are prokaryotes
Early Life
• Eukaryote
– An organism composed
of eukaryotic cells-
– Cells have a well defined
nucleus
4
Evolution and the Fossil Record
• Evolution
– The theory that life on
earth has developed
gradually, from one or a
few simple organisms
to more complex
organisms
– Charles Darwin
• “On the Origin of
Species by Means of
Natural Selection”
• Natural selection
– Individuals that are well adapted to their environment have a
survival advantage
– They then pass on their favorable characteristics to their
offspring
• Species
– A population of genetically and/or morphologically similar
individuals that can interbreed and produce fertile offspring