B14- evolution 🦕

Question 1

What are fossils ?

Hint: found in

Answer 1

• fossils are the remains of organisms from millions of years ago, which are found in rocks

Question 2

Name the three ways fossils can form

Hint: absent

Answer 2

• fossils can form from parts of organisms that have not decayed, because one or more of the conditions needed for decay are absent
• fossils may form, when parts of organisms are [slowly] replaced by minerals as they decay
• and, fossils may form as preserved traces of organisms such as: footprints, burrows and rootlet traces [preserved spaces where roots where]

Question 3

Why might decay be absent ?

Hint: water

Answer 3

• the temperature may be too cold
• there may not be enough oxygen
• and, there may not be enough water

Question 4

Why can’t scientists be certain about how life began on Earth ?

Answer 4

• many early forms of life were soft-bodied organisms [didn’t have a shell or skeleton], which means they left few traces [few fossils] behind
• and most of the few traces that did form as fossils, have mainly been destroyed by geological activity, as there are changes to rocks in the Earth’s crust
• [so as there are very few fossils of the early forms of life, scientists cannot be certain about how life on Earth began]

Question 5

What does it mean for a species to be ‘extinct’ ?

Hint: remaining

Answer 5

• a species is extinct, when there are no remaining individuals of that species still alive

Question 6

Name the three factors that may contribute to the extinction of a species

Answer 6

• species can become extinct due to a catastrophic event [such as an asteroid colliding with the Earth, which eventually lead to the extinction of the dinosaurs]
• a species can become extinct if the environment changes [e.g- changes to weather patterns]
• and, a species can become extinct due to a new disease or a new predator, which kills all of the individuals of a species
• and a species can also become extinct, if a new more successful species evolves and competes with it [due to scare food or scare water]

Question 7

Why do bacteria evolve rapidly ?

Answer 7

• bacteria evolve rapidly because, they reproduce at a fast rate

Question 8

What are antibiotics used in ?

Answer 8

• antibiotics are widely used in medicine- to treat bacterial diseases
• antibiotics are also used in farming

Question 9

Why are antibiotics used in farming ? 🐖

Answer 9

• antibiotics are used in farming, to prevent animals from developing bacterial diseases

Question 10

How does antibiotic resistance happen ?

Answer 10

• a colony of bacteria have mutations of bacterial pathogens, which produce new strains
• some of these strains are resistant to antibiotics, so these strains survive and are not killed.
• these strains of bacteria now reproduce, so the population of the resistant strain rises.
• the resistant strain then spreads because, people are not immune to it and there is no effective treatment

Question 11

What is the first step of antibiotic resistance ?

Answer 11

• a colony of bacteria have mutations of bacterial pathogens, which produce new strains

Question 12

In antibiotic resistance, what happens to the new strains from mutations ?

Answer 12

• some of these strains are resistant to antibiotics, so these strains survive and are not killed.

Question 13

What happens to the resistant strain of bacteria, that are not killed ?

Answer 13

• these strains of bacteria now reproduce [without any competition from other bacteria] so the population of the resistant strain rises.

Question 14

What happens after the population of the resistant strain of bacteria rises ?

Answer 14

• the resistant strain then spreads because, people are not immune to it and there is no effective treatment

Question 15

How can the rate of development of antibiotic resistant strains of bacteria, being reduced ?

Answer 15

• doctors should not prescribe antibiotics inappropriately [e.g- to treat viral infections, as antibiotics only kill bacteria]
• patients should complete their course of antibiotics, so all bacteria are killed and none survive to mutate and form resistant strains
• and, the agricultural use of antibiotics should be restricted [to prevent the spread of antibiotic resistance from animal to human pathogens]

Question 16

Why can’t researchers keep up with the emergence of new antibiotic resistant strains ?

Answer 16

• the development of new antibiotics is costly and slow, which means it is unlikely to keep up with the emergence of new resistant strains

Question 17

Who classified species into different categories, based on their structure and characteristics ?

Answer 17

• In the 1800s, the biologist Carl Linnaeus classified species into different categories, based on their structure and characteristics

Question 18

How were living things originally classified ?

Answer 18

• living things were originally classified [by Carl Linnaeus] into: kingdom, phylum, class, order, family, genus and species
• [remember the mnemonic: kids prefer cheese over fried green spinach]

Question 19

What two kingdoms were all living things originally divided into ?

Answer 19

• Carl Linnaeus divided all living organisms into two kingdoms: plant and animal kingdoms
• and he then divided each kingdom into smaller categories, which is known as his classification system

Question 20

How are organisms named ?

Answer 20

• organisms are named by the binomial [two names] system of genus and species
• [this means a species first name will be its genus, and its second name will be its species]

Question 21

Why have new models of classification be proposed ?

Answer 21

• new models of classification have been proposed because:
• internal structures have become developed due to an improvement in microscopes.
• and the understanding of biochemical processes have progressed [as an organisms’ DNA can be analysed]

Question 22

What is the three domain system ?

Answer 22

• the three domain system, is a new classification system developed by Carl Woese, who compared the biochemistry of different organisms
• Carl Woese, divided organisms into: archaea, bacteria and eukaryota

Question 23

In the three domain system, what are archaea ?

Answer 23

• archaea, are primitive bacteria typically living in extreme conditions [such as hot springs and salt lakes]

Question 24

In the three domain system, what are bacteria ?

Answer 24

• the bacteria domain contains ‘true bacteria’, such as E.coli and they can live in the human digestive system
• true bacteria look similar to archaea [primitive bacteria]; there are multiple biochemical differences between them

Question 25

In the three domain system, what are eukaryota ?

Answer 25

• the eukaryota domain includes protists [e.g- amoeba], fungi, plants and animals.

Question 26

What are evolutionary trees ?

Answer 26

• evolutionary trees are a method used by scientists, to show how closely related organisms are to each other

Question 27

How are evolutionary trees made ?

Answer 27

• to make an evolutionary tree, scientists can use their classification data on living organisms [e.g- DNA]
• ; for extinct organisms, scientists have to use fossils, which present a promblem

Question 28

When making evolutionary trees, why are using fossils a promblem ?

Answer 28

• the fossil records of many species are incomplete because, there are very few fossils of the early forms of life