History Of Life

Question 1

Scientists estimate that the earth came into existence approximately

Answer 1

4,6 billion years ago

Question 2

Scientists estimate that the earth came into existence approximately

Answer 2

4,6 billion years ago

Question 3

Life on earth began

Answer 3

3,8 billion years ago 2ith a unicellular, prokaryotic cell similar to a bacterial cell. Multicellular cells developed a few billion years later.

Question 4

Scientists try to make sense of history of life on earth by relating it to important events like

Answer 4

The increase in oxygen levels in the Earth’s atmosphere
Climate change like ice ages
Geological events like the continental drift
Fossil evidence

Question 5

Increase in energy levels

Answer 5

When earth was formed, the oxygen levels were very low. Modern theories suggest that the first life forms ege the prokaryotes which appeared 3,8 billion years ago didn’t need oxygen. They respired anaerobically and therefore obtained energy from their food without using oxygen.
When different bacterias arose that could produce their own food through the process of photosynthesis, carbon dioxide which occurred in large quantities in the atmosphere was used which made and released oxygen. The increase in oxygen levels in the atmosphere resulted in an increased variety of living organisms of earth

Question 6

Climate change

Answer 6

Iice ages are long Geological periods of drastic decrease in the temperature of the Earth’s surface and atmosphere.
Glaciation takes place because large ice sheets form due to the cooling temperatures
At least 4 ice ages occurred since the origin to earth.
During the ice ages many species that could not adapt to the low temperatures died out.
Some species were forced to migrate towards the equator where the temperatures were higher.
The climate was drier because most of the water was trapped in snow and ice. Many terrestrial species became extinct due to the dry climate.
Due to the ice formation the sea level dropped resulting in the decreased habitats and the extinction of many aquatic species.
Ice ages therefore affected life on earth due to the extinction and redistribution of species

Question 7

Geological events

Answer 7

Up until 200 million years ago all continents were fused to form one giant continent, PANGAEA which broke into two super continents :LAURASIA IN THE NORTH AND GONDWANALAND IN THE SOUTH.
As a result of the continental drift the climate changed. Habitats also changed or were destroyed. A large number of life forms became extinct or had to adapt to the changing environment. By means of biogeography, evidence had been found that the continents wee once joined. Closely relate species occurring on different continents probably shared a common ancestor

Question 8

Biogeography

Answer 8

Study of the distribution of existing and extinct plant and animal species in specific geographical regions on earth. Example :ostrich in Africa and emu in austand nandu in south America

Question 9

Scientists claimed that flightless birds

Answer 9

May have been developed from a common ancestor and that when the birds were separated geographically when GONDWANALAND broke apart. The flightless birds probably adapted to the changing environment and new species developed.

Question 10

Fossil evidence

Answer 10

Fossils are complete organisms or the remains, imprints or traces/tracks of organisms usually preserved in rock.
Remains of ancient life that has been preserved in rock.
Fosssils provide evidence of earlier life(extinct organisms) on earth and give information regarding the history of life on earth. Fossils also give indications of the climate and the environment of millions of years ago.
Examples of fossil evidence include the fossils of bivalve(mussel) and ammonite.

Question 11

The study of plant and animal fossils is known as……. And a scientist who studies fossils is a….

Answer 11

Palaeontology
Palaeontologist

Question 12

Bivalve

Answer 12

A marine/freshwater snail with a soft body that is compressed in a shell consisting of two separate parts that is joined with a strong flexible muscular hinge ege oysters.

Question 13

Ammonite

Answer 13

An extinct marine snail with a flat spiral shell divided into chambers with wavy interlcoking walls and became extinct about 65mya

Question 14

Trilobites (found in karoo)

Answer 14

Extinct arthropods, their bodies divided into horizontal segments and three vertical loves. Related to crabs and lobsters and became extinct 250 Mya.

Question 15

Whale fossils discovered in

Answer 15

The Sahara desert.

Question 16

Geological timescale

Answer 16

The purpose of it is to represent a time line of life on earth from the origin of the earth. Time units are divided according to the age of the fossils that have been discovered. The largest defined unit of time is the aeon divided into 3 eras: palaeozoic, mesozoic and cenozoic. And each for these is further divided into periods:quaternary, tertiary and cretaceous.

Question 17

Fossil record

Answer 17

Alll the fossils of different ages that have been discovered by palaeontologists are listed. However they are incomplete and don’t have an indication of all the organisms that lives a particular period.

Question 18

Archaeopteryx

Answer 18

Transitional fossil known as the earliest and primitive bird displaying both characteristics of a bird and reptile.

Question 19

Characteristics of reptiles

Answer 19

Sharp teeth in sockets
Finger with claws.
Long bony tail

Question 20

Characteristics of bird

Answer 20

Feathers
Wihs bond for attachment of muscles for flight.

Question 21

Marine fossils

Answer 21

Fossils found in the ocean

Question 22

Glaciers

Answer 22

Large masses of ice.

Question 23

Anaerobic

Answer 23

Respiration that occurs in the absence of oxygen.

Question 24

The three main Eras of Earths history. dividing the geological time scale

Answer 24

Paleozoic, Mesozoic and Caenozoic

Question 25

continental drift –

Answer 25

the theory that the continents were once all joined together and have slowly moved apart over millions of years.

Question 26

convection currents

Answer 26

Circular currents in the mantle created by the rising of hot magma and sinking of cool magma. These currents cause tectonic plates to move.

Question 27

crust –

Answer 27

The thin, rocky, outer layer of the Earth.

Question 28

seafloor spreading –

Answer 28

The movement of two oceanic plates away from each other, which results in the formation of new oceanic crust and a mid-ocean ridge.

Question 29

what causes extinction

Answer 29

The environment changes (eg. climate warms up)
A competitor moves into the habitat and takes food / nesting sites.
A predator moves into the habitat
diseases
Another plant or animal in the food web becomes extinct.

Question 30

The British naturalist Charles Darwin (1809–1882) later suggested a more persuasive argument for evolution.

Answer 30

Darwin proposed that evolution took place through natural and sexual selection.

Question 31

Darwin developed his theory of evolution after noticing

Answer 31

close similarities between certain fossils and the adaptations of modern day animals he saw during his round-the-world voyage on the HMS Beagle.

Question 32

However, when Darwin learned that another British naturalist,

Answer 32

Alfred Russel Wallace, had proposed an almost identical theory of natural selection, he published his findings.

Question 33

evolution

Answer 33

The development of new species as a result of natural selection.

Question 34

extinction

Answer 34

The complete disappearance of a species due to changes in its environment that reduce its ability to survive and reproduce.

Question 35

fossil

Answer 35

The preserved remains, impressions or traces of an organism that lived millions of years ago

Question 36

natural selection –

Answer 36

The process where individuals that are well adapted to their environment survive and reproduce at the expense of less well-adapted individuals.

Question 37

trait

Answer 37

A distinguishing and inheritable characteristic of an organism.

Question 38

variation

Answer 38

The natural differences between individual members of a species.

Question 39

he formed the theory that

Answer 39

organisms evolve to adapt to their environment and organisms with adaptive features allows survival and reproduction of the species that will live while the others die out

Question 40

What happens when habitats change?

Answer 40

Adaptive evolution ensures that individuals within a species have traits allowing them to survive and reproduce in their habitat.
if the habitat changes, however, successful traits can become a disadvantage.Individuals that fail to reproduce, compete effectively for food or survive against new predators will eventually die out. If the last individual of a species dies, the species is extinct.

Question 41

why did the dodo become extinct

Answer 41

The dodo was a large flightless bird that lived on the island of Mauritius.
It nested on the ground in forests, producing one egg at a time.When human settlers arrived on the island in the mid-1600s, they brought animals such as rats and dogs to the island, which ate the dodos’ eggs.The settlers chopped down the forests in which the dodos lived, and may have even hunted the dodo for food.

Question 42

what could have hepled dodo survive

Answer 42

The dodo’s large size and inability to fly were adaptations that allowed this bird to survive

Question 43

purpose of geological timescale

Answer 43

represent a timeline of life on earth from the origin of earth

Question 44

What is the theory of plate tectonics?

Answer 44

he explanation for how the continents move came from observations of seafloor spreading and other effects. In 1967, these ideas were linked in the theory of plate the Earth’s crust is like a jigsaw puzzle made up of giant sections called tectonic plates.
These plates ‘float’ on top of the mantle and so can move around the Earth’s surface.

Question 45

pangea