Animals Evolutionary History and Diversification

Bio 2.2 Zoology, discussing what happens in the eons and eras.

What are the 4 Eons on Earth?

1. Hadean

2. Archean

3. Proterozoic

4. Phanerozoic

How long ago did the Hadean Eon occur?

4.6-4.0 billion years ago(bya)

How long ago did the Archean Eon occur?

4.0 bya-2.5bya

How long ago did the Proterozoic Eon occur?

2.5bya- 541mya

How long ago did the Phanerozoic Eon occur?

541mya-present day

Which Eon has 3 Eras?

Phanerozoic

What were some key events during the Hadean Eon?

• There were no life forms

• Earth was cooling down

What were some key events during the Archean Eon?

• first prokaryotes 3.5-3.8 bya

• autotrophs, did photosynthesis

• began to release oxygen as a byproduct 2.7 bya

What were some key events during the Proterozoic Eon?

• Great Oxygenation 2.4 bya

• Single Celled Eukaryotes appeared 1.8 bya

• multicellular eukaryotes appeared 1.65 bya

• first animals appeared the Ediacaran fauna 635 mya-541 mya

• molecular clock of sponges 700 mya

• fist sponge fossil 550 mya

What type of Eukaryotes were present in the Proterozoic eon?

• single cell eukaryotes

• colonial cells

• multicellular eukaryotes

What are colonial cells?

Cells that can live on their own or together.

When did the first multicellular eukaryotes appear?

1.65 bya according to a discover made in China

When did the first animals appear?

the Ediacaran Fauna first appeared 635-541mya

What species are animals closely related too?

Choanoflagellates

How do we know Choanoflagellates are closely rated to animals?

Do to DNA evidence like the Cadherin proteins and collar cells

What domain is different in the Choanoflagellates and animals?

A. CDD

B.CCD

C. DDC

D. CDC

B, CCD

Are Choanoflagellates our sister group or out group?

It depend on the level you are looking at.

Which animals do scientists think are the first animals?

A jellyfish

B. Choanoflagellates

C. Coral

D. Sponges

D. Sponges

When did Sponges first get discovered?

700 mya

When was the first sponge fossil found

550 mya

When was the first sign of predation occur?

Bore holes found in a skeleton from ediacaran fauna

What marked the beginning of the Phanerozoic eon?

• extinction of Ediacaran Fauna

• Rise of bilateral animals

• Another oxygenation period.

What are the three eras in Phanerozoic eon?

1. Paleozoic

2. Mesozoic

3. Cenozoic

What event marked the beginning of the Paleozoic era?

The Cambrian Explosion

How long ago did the Cambrian Explosion occur?

535- 525 mya

Why did the Cambrian Explosion occur?

• Another oxygenation period

• HOX gene duplicates

  increased minerals in water

Why was it a big deal that the Cambrian Explosion happened

Lead to rise of bilateral animals that we are still related to today.

What marked the end of the Paleozoic era?

the great dying

What was the mesozoic era known as? What was the time frame?

the age of reptiles. 252-66 mya

What marked the beginning of the Cenozoic era?

The asteroid causing the extinction of dinosaurs.

What is the Cenozoic era known as? what is the time frame?

the age of mammals.66 mya- today.

Who was the first animal and why?

The sponge is the first animal due to DNA evidence like choanocytes and cadderin proteins which resemble choanflagellates collar cells.

State which organisms are the outgrip to animals and what evidence links us to these organisms. 

Choanoflagelllts are the out group to animals because they are colonial cells who have collar cells, cadherin proteins, and collagen depending on DNA evidence. 

Explain what the Cambrian Explosion was?

The Cambrian explosion lead to the rise of bilateral animals and a lot more animal diversity.

Why was the Cambrian explosion a big deal ?

We are closely related too many of the animals from this era.

What are the possible explanations for the Cambrian explosion?

more atmospheric oxygen, duplication in hox genes, increased minerals in water which lead to the development of more hard parts. 

What is the difference between Ediacaran and cambrian animals

There were less ediacaran fauna and many of them were sessile. Cambrian animals were mobile, active predation, and had limbs.