History of Earth

Question 1

What is a geological time scale?

Answer 1

A geological timescale is a timescale of all critical events, like mass extinctions, Volcanic eruptions, and earthquakes. They are based on the studies of earth’s geology and the fossil record. We use it to describe when events happened in the history of the earth.

Question 2

What is relative dating?

Answer 2

Relative dating is finding out the dates or years using rock layers. The bottom-most layer is the oldest and the top most is the youngest. We can’t get precise dates with this.

Question 3

How are time periods divided?

Answer 3

Time periods are divided into Eons, Era, Periods, epochs, and ages.

Question 4

Describe the Precambrian era

Answer 4

The Precambrian era was from 4.6 billion years ago to 542 million. First prokaryotic cells were formed. Cyanobacteria came to life. Oxygen was let out creating, the ozone layer was formed at lower temperatures. First eukaryotic cells also came in this time about 2 billion years ago.

Question 5

Describe the Paleozoic era

Answer 5

The paleozioc era was 542 to 251 million years ago. This is ancient life. At this time, fossils of trilobites, snails, clams, and corals were found. Complex organisms formed, such as fishes with backbones, air-breathing animals, and plants. Therapids dominated at this time

Question 6

Describe the Mesozoic era

Answer 6

The Mesozoic era was 251 to 61 million years ago. It was middle life. This time was marked by the Jurrasic period and the appearance of first birds. It was the age of reptiles. Flowering plants evolved. In the end, animal and plant species became extinct because of the asteroid

Question 7

Describe the Cenozoic era

Answer 7

The Cenozoic era started 65 million years ago and is still going on. It is the age of mammals. It is recent life. Human ancestors appeared about 4 million years ago and modern humans about 40,000 years ago. Eohippus appeared in this era.

Question 8

What are fossils?

Answer 8

Remains or traces of organisms.

Question 9

Why don’t most organisms become fossils?

Answer 9

Because when an organism dies, scavengers usually eat the flesh and the bones usually disintegrate to become dust.

Question 10

What are the two types of fossils?

Answer 10

Body fossils: Organism’s body parts or remains. Ex: shells, bones
Trace fossils: evidence of an organism through its activity. Ex: Footprints

Question 11

Where are some of the best-preserved fossils found?

Answer 11

In unusual conditions and in rock beds.

Question 12

Describe the formation of fossils

Answer 12

1. Death
2. No decaying
3. Quick burial
4. Layers of sediments
5. Compression
6. minerals
7. time

Question 13

Due to which event did many species evolve?

Answer 13

Cambrian explosion

Question 14

Extinction

Answer 14

Extinctions occur when the environment changes and the adaptations of the species are no longer sufficient for its survival. Most species that once lived on Earth are now extinct.

Question 15

What was the permian extinction?

Answer 15

The permian extinction was about 250 million years ago in the end of the Palezoic era. Particles of dust were send into the atmosphere and there were Longterm & shorterm changes for organsims at the time. Scientists believe it could be a volcano or a asteroid.

Question 16

What was the Cretaceous-tertiary extinction?

Answer 16

It occured about 65 million years ago in the end of the mesozoic era. Scientists believe it was an asteroid. Dust went into the atmosphere. The sun was blocked out. Changes in climate and habitat caused the extinction of the dinosaurs. Birds were the only species to survive. Mammals became dominant species after them

Question 17

What are bacteria?

Answer 17

Bacteria are the only prokaryotes Bacteria are organisms that consist of a single, prokaryotic cell. Bacteria are the only prokaryotes (cells without a nucleus). All other life forms on Earth are eukaryotes

Question 18

Shapes of bacteria

Answer 18

Bacteria are often described according to the shape of their cells. Rod-shaped bacteria are
called bacilli. Ball-shaped bacteria are called cocci. Spiral-shaped bacteria are called spirilla.

Question 19

Bacteria’s symbiosis

Answer 19

Many kinds of bacteria have developed close relationships with other organisms. In many relationships the bacteria and the organism it lives with benefit. This type of symbiosis is called
mutualism.

Question 20

Principle of Uniformitarianism

Answer 20

ou may need to apply what you know about the present to determine what happened in the past.
The idea that the present is the key to the past was recognized by James Hutton in the late 1700s.
If you see something forming by a process today and then find the end result of that process in the rock record, you can assume that the process operated the same way in the past.

Question 21

What is the principle of superposition?

Answer 21

In and undisturbed layer of rocks, the rocks are the bottom are the oldest and the rocks at the top are the youngest.

Question 22

What is absolute dating?

Answer 22

When we use radioactive decay of radioactive minerals in rocks to determine the age of the rocks, when an element decays, it becomes a new element because of isotopes. In its first half-life, half of it would have changed in its second half-life 1/4 of it would’ve changed, and so on. With this scientists can find out the exact age of the rock, this is called radiometric dating.

Question 22

What is absolute dating?

Answer 22

When we use radioactive decay of radioactive minerals in rocks to determine the age of the rocks, when an element decays, it becomes a new element because of isotopes. In its first half-life, half of it would have changed in its second half-life 1/4 of it would’ve changed, and so on. With this scientists can find out the exact age of the rock, this is called radiometric dating.

Question 23

How many bones do a baby and an adult have?

Answer 23

Baby - 300
Adult - 206

Question 24

What are cartilages?

Answer 24

Cartilages are dense connective tissues that are at the end of both sides of a bone. They are made of tough protein fibers and slowly fuse as the human body gets older. It allows bones to have a smooth movement.

Question 25

What are the functions of the skeletal system?

Answer 25

The functions of the skeletal system are:
1. To protect soft organs
2. To store calcium and phosphorous
3. To help in movement with muscles
4. To make blood cells
5. To support the body.

Question 26

Structures of bones

Answer 26

1. Periosteum - The shiny outer layer of the bone
2. Compact bone - The dense layer of the bone under the periosteum
3. Cancelleous/Spongy bone - The less dense, and porous layer under the compact bone
4. Bone marrow - Soft tissue in the pores of the spongy bone that makes blood cells.

Question 27

How is the skeleton divided?

Answer 27

Axial skeleton - Bones that form the axis of the body. Skull to the rib cage.

Appendicular skeleton - Bones that form your arms, pelvic bone and limbs

Question 28

Joints

Answer 28

Fixed joints - Skull
Hinge joints - One-way movement. Ex: Elbows, knees
Ball and socket joints - Allow full movement. Ex: Shoulders
Sliding joints - Flexible joints that can slide past and over one other. Joints in the hand.