B15

Question 1

What did Gregor Mendel do?

Answer 1

• Until 150 years ago people had no idea how genetic information was passed on from one generation to the next.
• Mendel studies peas and carried out breeding experiments.
• He used smooth, wrinkled, green and yellow peas for his work.
• He cross-bred the peas and counted the different offspring carefully.
• He notes his observations.
• He found characteristics were inherited in a clear and predictable pattern

Question 2

What did Gregor Mendel realise?

Answer 2

• Realised some characteristics were dominant over others
• They NEVER mixed together
• DNA, Chromosomes, genes had not yet been discovered.
• Mendel published his findings in 1866
• He used mathematical models to explain basic laws of genetics e.g. monohybrid inheritance (still used today)
• Mendel wasn’t acknowledged until after his death

Question 3

Why did people not accept mendels idea when it was first published ?

Answer 3

1. People couldn’t see units of inheritance, so no proof of their existence.
2. People were unused to studying careful records of results.

Question 4

How did the development of the microscope play a important part in helping to convince people that Mendel was right ?

Answer 4

1. Microscopes enabled people to see chromosomes cell nucleus
2. and observe chromosome movement in meiosis.
3. This proved mechanism for Mendel’s principles of inhertitance, promoting it’s acceptance

Question 5

What was Jean-Baptiste Lamarck’s theory of evolution? Skip this one

Answer 5

-Theory of evolution based on the complexifying force and the adaptive force.

-His idea was that every type of animal evolved from primitive worms. The change from worms to other organisms was caused by the inheritance of acquired characteristics.

-If animals used something a lot over a lifetime, Lamarck thought this feature would grow and develop. Any useful changes that took place in an organism during its lifetime would be passed from a parent to its offspring.

-People could also see quite clearly that changes in their bodies - such as big muscles, for example - were not passed on to their children.

Question 6

What was Charles Dawin’s theory of evolution?

Answer 6

-Organisms can only pass on traits they are born with

-There is variation within a species.

-Certain traits helped organism survive better than organisms without those traits

-The environment has something to do with why organisms change

-Natural selection

-Species have changed over time

Question 7

What was Jean Baptiste Lamarck’s theory of evolution ?

Answer 7

-Parents can pass on changes made in their lifetime to their offspring
-Organisms change because they want to survive
-The environment has something to do with why organisms change
-Acquired characteristics
-Species have changed over time

Question 8

Why did people not agree with Dawin?

Answer 8

-It went against common religious beliefs about how life on Earth developed - it was the first plausible explanation for the existence of life on earth without the need for a “Creator” (God). Which made it very controversial

-Darwin couldn’t explain why these new, useful characteristics appeared or how they were passed on from individual organisms to their offspring. But then he didn’t know anything about genes or mutations they weren’t discovered ‘til 50 years after his theory was published.

-There wasn’t enough evidence to convince many scientists, because not many other studies had been done into how organisms change over time.

Question 9

What is speciation?

Answer 9

Over a long period of time, the phenotype of organisms can change so much because of natural selection that a completely new species is formed. This is called speciation

Question 10

Why do species become extinct?

Answer 10

-the envirnoment changes too much (e.g. destruction of habitat)
-a new predator kills them all
-a new disease kills them all
-they cant compete with another (new) species of food
-a catastrohic event happens that kills them all

Question 11

How does isolation and natural selection lead to speciation ?

Answer 11

Isolation is where populations of a species are separated. This can happen due to a physical barier.
E. g. floods and earthquakes can cause bartiers that geotraphically isolate some individuals from the main population. Conditions on either side of the barrier will be slightly different, e.g. they may have different climates. Because the environment is different on each side, different oharacteristios will become more common in each population due to natural selection operating differently on the populations.

Eventually, individuals from the different populations will have changed so much that they won’t be able to breed with one another to produce fertile offspring. The two groups will have become separate species.

Question 12

How has Darwin’s theory of evolution been evidenced ?

Answer 12

Darwin’s theory of evolution by natural selection has been evidenced in fossils.

Question 13

When did life begin around ?

Answer 13

It is presumed that it was 3-4 billion years ago

Question 14

What are fossils ?

Answer 14

Fossils are the remains of organisms from millions of years ago that are found preserved in rocks or ice.

Question 15

How do fossils form ?

Answer 15

Animal or plant does not decay after it has died. Conditions needed for decay are not present (little /no oxygen, poisonous gas kills bacteria that cause decay).
Or when harder parts of the animal or plant are replaced by minerals as they decay → rock

Fossils may be formed:
• from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
• when parts of the organism are replaced by minerals as they decay
• as preserved traces of organisms, such as footprints, burrows and rootlet traces.

Question 16

What is the step by step method of how a fossil forms ?

Answer 16

1) the reptile dies and falls to the ground
2) the flesh rots, leaving the skeleton to be covered in sand or soil and clay before it’s damaged
3) protected over millions of years, the skeleton becomes mineralised and turns to rock. The rocks shift in the earth with the fossils trapped inside
4) Eventually, the fossil emerges as the rocks move and erosion takes place

Question 17

What conditions could cause fossilisation ?

Answer 17

-lack of oxygen
-absence of bacteria
-extreme cold temperatures

Question 18

How do fossil records help scientists ?

Answer 18

Fossil records help scientists understand how much organisms have changed since life developed on earth

Question 19

What is extinction ?

Answer 19

Extinction is the permanent loss of all members of a species.

Question 20

What can extinction be caused by ?

Answer 20

-new predators
-new diseases
-more sucessfull competitors

Question 21

What are the biggest influences on survival ?

Answer 21

-changes in the environment over geological time
-or single catastrophic event

Question 22

What are the causes of mass extinction ? How do these impact the world ?

Answer 22

• Evidence suggests that a single catastrophic event is often the cause of mass extinctions.
• E.g. volcanic eruption, asteroid collision.
• These impacts also affect the climate over a long period of time, this impacts extinction rates.

Question 23

How are bacteria resistant strains made ? And how do they impact us ?

Answer 23

Mutations of bacterial pathogens produce new strains. Some strains might be resistant to antibiotics, and so are not killed. They survive and reproduce, so the population of the resistant strain rises. The resistant strain will then spread because people are not immune to it and there is no effective treatment.

Question 24

How can we prevent resistant strains of bacteria developing ?

Answer 24

• Do not overuse antibiotics e.g. do not prescribe antibiotics for cold/flu.
• Complete the full course of antibiotics
• Restrict agricultural use of antibiotics-do not use human antibiotics on farm animals.

Question 25

What is classification ?

Answer 25

Classification is organising living organisms into groups.

Question 26

What did Carl Linnaeus do?

Answer 26

Traditionally, organisms have been classified according to a system first proposed in the 1700’s by Carl Linnaeus, which groups living things according to their characteristics and the structures that make them up.

Question 27

What’s the Linnaen system divided into ?

Answer 27

-In this system (known as the Linnaean system, living things are first divided into kinsdoms (e.g. the plant kingdom).

-The kingdoms are then subdivided into smaller and smaller groups - phulum, class, order, family, genus, species.

Question 28

How did classification systems change over time ?

Answer 28

-As knowledge of the biochemical processes taking place inside organisms developed and microsoopes improved (which allowed us to find out more about the internal structures of organisms), scientists put forward new models of classification.

-In 1990, Carl Woese proposed the three-domain system. Using evidence gathered from new chemical analysis techniques such as RNA sequence analysis, he found that in some cases, species thought to be closely related in traditional classification systems are in fact not as closely related as first thought.

Question 29

What are the domains in the three-domain system ?

Answer 29

In the three-domain system, organisms are first of all split into three large groups called domains:
1)ARCHAEA
- Organisms in this domain were once thought to be primitive bacteria.
but they’re actually a different type of prokaryotic cell. They were first found in extreme places such as hot springs and salt lakes.

2) BACTERIA
- This domain contains true bacteria like E. coli and Staphylococcus. Although they
offen look similar to Archaea, there are lots of biochemical differences between them.

3) EUKARYOTA - This domain includes a broad range of organisms including fungi, plants, animals and protists

These are then subdivided into smaller - kingdom, phylum, class, order, family, genus, species

Question 30

What are organisms named according to?

Answer 30

Organisms are named according to the binomial system

Question 31

What is the binomial system ?

Answer 31

1)In the binomial system, every organism is given its own two-part Latin name.

2) The first part refers to the genus that the organism belongs to. This gives you information on the organism’s ancestry. The second part refers to the species. For e.g. We humans are known as homosapiens ‘Homo’ is the genus and ‘sapiens’ is the species.

Question 32

When writing scientific names such as Homo sapiens what are the rules for writing these?

Answer 32

-Genus (starts with a capital)
-Species (starts with a lower case)

-normally written in Italics
Or
-if by hand then the genus and species has to be underlined

Question 33

Why is the binomial system used ?

Answer 33

It is used worldwide and if means that scientists in different countries or who speak different languages all refer to a particular species by the same name - avoiding potential confusion

Question 34

What do evolutionary trees show ?

Answer 34

-Evolutionary trees show how scientists think different species are related to each other

-They show common ancestors and relationships between species.
The more recent the common ancestor, the more closely related the two species - and the more characteristics they’re likely to share.

Question 35

How do scientists analyse lots of different types of data to work out evolutionary relationships for living organisms and for extinct species ?

Answer 35

For living organisms, they use the current classification data (e.g. DNA analysis and structural similarities).

For extinct species, they use information from the fossil record

Question 36

Who and why created the three-domain system ?

Answer 36

In 1990, Carl Woese proposed the three-domain sustem.

Using evidence gathered from new chemical analysis techniques such as RNA sequence analysis, he found that in some cases, species thought to be closely related in traditional classification systems are in fact not as closely related as first thought.