1. History of Invertebrates
Bonneville High School
Mr. Walker

2. Water and Life
The origin and maintenance of life on earth depends on water.
Allows the basic biomolecules.
Lipids
Carbohydrates
Nucleic Acids
Proteins

3. How life began Two Theories:
Spontaneous Generation: Living things can come from other non-living things
Biogenesis: Living things can come from other living things.

4. Experiments:
Experiments by Louis Pasteur in the 1860s convinced scientists that organisms do not arise repeatedly from inorganic matter.
About 60 years later, A. I. Oparin and J. B. S. Haldane provided an explanation for how a common ancestor of all living forms could have arisen from nonliving matter almost 4 billion years ago.
The origin of life followed a long period of “abiogenic molecular evolution” on earth in which organic molecules slowly accumulated in a “primordial soup.” The atmosphere of the primitive earth was reducing, with little or no free oxygen present. Ultraviolet radiation, electrical discharges of lightning, or energy from hydrothermal vents could have provided energy for early formation of organic molecules.
Stanley Miller and Harold Urey demonstrated the plausibility of the Oparin-Haldane hypothesis by simple but ingenious experiments. The concentration of reactants necessary for early synthesis of organic molecules might have been provided by damp surfaces, clay particles, iron pyrite, or other conditions. RNA might have been the primordial biomolecule, performing the functions of both genetic coding of information and catalysis. When self-replicating systems became established, evolution by natural selection could have increased their diversity and complexity.

5. Prokaryotes
The earliest bacterium like organisms developed about 3 billion years ago.
These bacterium (cyanobacteria) were capable of producing oxygen through photosynthesis.
These organisms rules the oceans for 1-2 billion years. They evolved into true bacteria (eubacteria) and algae.

6. PRECAMBRIAN LIFE
The Precambrian period covers the geological time before the beginning of the Cambrian period some 570 to 600 million years ago.
Most major animal phyla appear in the fossil record within a few million years at the beginning of the Cambrian period.
This appearance has been called the “Cambrian explosion” because before this time, fossil deposits are mostly devoid of any organisms
more complex than single-celled bacteria.

7. Appearance of Eukaryotes
These cells have a nucleus and membrane bound organelles. They contain chromatin (DNA wrapped around proteins called histones).
Single celled eukaryotes arose at least 1.5 billion years ago.
The first eukaryotes evolved to be carnivorous and photosynthetic.
This ended the Precambrian period and the beginning of the Cambrian period.

8. Phylogentic Relationships of Animals
Platyhelminthes
Porifera
Mollusca
Chordata
Arthropoda
Annelida
Cnideria
Nematoda
Echinodermata
pseudocoelom
segmentation
acoelom
Protostome: schizocoelem
Deuterostomes:
eucoelom
radial symmetry
bilateral symmetry
no true tissues
true tissue
Ancestral Protist

10. Origins of Animal Diversity
Based on anatomical and embryological criteria, there are about 35 phyla.
Most major animal body plans appeared between 525 million to 545 million years ago during the late Precambrian and Paleozoic eras.
A lot of the more advanced invertebrates appeared in the Cambrian and Ordovician periods within the Paleozoic Era.

11. Why not evolve quickly?
The burst of evolutionary activity that followed at the end of the Precambrian period and beginning of the Cambrian period was unprecedented.
Some investigators hypothesize that the explanation for the “Cambrian explosion” lies in the accumulation of oxygen in the atmosphere to a critical threshold level.
Larger, multicellular animals required the increased efficiency of oxidative metabolism; these pathways could not be supported under conditions of limiting oxygen concentration.