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1

Four Eras of Time

Precambrian, Paleozoic, Mesozoic, Cenozoic

2

The principle of common ancestry

States that all life on earth can be traced back to a single ancestor

3

Fossil

The remains or traces of past life usually preserved in sedimentary rock

4

Parts of the geological timescale

Eras, Periods, Epochs

5

Geological timescale

Divides the history of the earth into eras, periods, and epochs.

6

Stromatolites

Boulders from the Precambrian era

7

How much of the geological timescale does the Precambrian era contain?

87%

8

3.8 BYA

First chemical fingerprints of complex cells occur

9

3.46 BYA

Photosynthetic prokaryotic cells appear

10

What did early bacteria resemble?

The Arcae that live in Hot Springs today

11

What did early stromatolites resemble?

Living stromatolites with cyanobacteria on the outer surface

12

2 BYA

Oxygen levels were high enough that Anaerobic prokaryotes where declining.

13

Excessive oxygen gas caused…

Extinction of anaerobic organisms and the rise of aerobic organisms.

14

Oxygen gas forms the ozone shield (O3) in the upper atmosphere contributing to…

The blocking of ultraviolet radiation from reaching the earth surface allowing organisms to live on land

15

Eukaryotic Cells

Arose 2.1 BYA

Aerobic

Contains a nucleus and organelles

16

Endosymbiotic theory

States that a nucleated cell probably engulfed prokaryotes which then became organelles

Mitochondria were probably free living aerobic prokaryotes

Chloroplasts were probably free living photosynthetic prokaryotes

Cilia and flagella may have originated from slender undulating prokaryotes that attached to host cells.

17

Support for the Endosymbiotic theory

Mitochondria and chloroplasts have a similar size of that of bacteria.

Mitochondria and chloroplasts have their own DNA and make some of their own proteins.

Mitochondria and chloroplasts divide by binary fission similar to bacteria

Their outer membranes differ:
The outer - eukaryotic, the inner - prokaryotic

18

Multicellularity Arises

Not known exactly what multicellular organisms appeared. (approximately 1.4 BYA)

They were initially microscopic

The separation of germ cells from somatic cells may have helped with the diversity of organisms

Early multicellular organisms lacked internal organs and could have absorbed nutrients from the sea

19

Stages to become a protist

Unicellular
colony
specialization
gametes
protist

20

The Paleozoic era

Known as the Cambrian explosion
Lasted over 300 million years
Had three major mass extinctions (ex. Trilobites)

21

Cambrian animals

The Cambrian period saw invertebrates flourish
Cambrian sea floors were dominated by trilobites that had armored exoskeletons

22

Invasion of land

Life first begin to move out of the ocean around 500 million years ago in the Paleozoic era

Spiders centipedes and millipedes all came before the appearance of insects on land

The vertebrate line of descent began in the early Ordovician period.

The Devonian period is called the age of fish.

The Carboniferous was an age of coal forming forests.

23

Amphibian diversification

Early vascular plants and amphibians were larger and more abundant during the Carboniferous period.

The climate change to colder and drier begin the process that produced coal.

24

Mesozoic era (The Triassic Period)

Reptiles and went adaptive radiation

One group of reptiles, the therapsids, had mammalian traits.

25

The Jurassic period

Many dinosaurs flourished in the sea, on land, and in air

26

The Crustaceous period

The era of dinosaurs ended in a mass extinction in which dinosaurs, most reptiles, and many marine organisms perished.

27

The Cenozoic era

Mammals with hair and mammory glands diversified and human evolution began

28

Mammalian diversification

Early on mammals were small.

The modern orders of mammals developed

Many of the types of herbivores and carnivores of the Oligocene Epoch are extinct today.

29

Evolution of primates

The first primates were small squirrel- like animals; they evolved into the first monkeys and apes

Apes diversified during the Miocene and Pliocene epochs; this includes the first hominids, the group that includes humans.

30

Tertiary Period

The worlds climate cooled with the last two epochs known as the Ice Age