b15 - genetics and evolution

Question 1

how old is earth and when did life begin?

Answer 1

• scientists believe Earth is 4500 million years old
• believe that life began 3500 million years ago

Question 2

how can we date when different organisms existed?

Answer 2

• we can date rocks
• fossils are found in rocks

Question 3

give 3 main ways fossils may be formed

Answer 3

• from hard part of animals that do not decay easily e.g: bones, teeth, shells, claws
• from parts of organisms that have not decayed because some of the conditions for decay are absent
• parts of organism being replaced by other materials

Question 4

why did most organisms that died not leave a fossil?

Answer 4

exact conditions for fossil formation were not present

Question 5

why aren’t there many traces of evolution?

Answer 5

• all been destroyed by geological activity like earthquakes

Question 6

why is the fossil record incomplete?

Answer 6

many early forms of life were soft-bodied, which means that they have left few traces behind

Question 7

give the process of a reptile fossil formation

Answer 7

1) reptile dies and fall to ground
2) flesh rots, skeleton covered in sand or soil and clay before damaged
3) protected over milions of years, skeletons become mineralised and turns to rock which shifts in earth with fossile inside
4) fossil emerges as rocks move and erosion takes place

Question 8

define extinction

Answer 8

species that once existed has completely died out

Question 9

give reasons of extinction

Answer 9

• new disease may kill all members of species
• environment changes over geological time
• new diseases may be introduced
• new predator may evolve or be introduced to an area that kills and eats all of a species
• new competitor may evolve or be introduced to an area that kills and eats all of a species
• single catastrophic event
• natural changes in species

Question 10

why might a species die out if the climate changes?

Answer 10

• conditions could be too hot or too cold, too wet or too dry, for a species and reduce food supply

Question 11

what does fossil evidence show us?

Answer 11

there has been mass extinctions on a global scale

Question 12

why did many species die out over a period of several million years?

Answer 12

• habitat the species live in may be destroyed by catastrophic events e.g: major volcanic eruption
• environment can change dramatically following a collision between a giant asteroid and earth

Question 13

give an idea relating to a collision as to why dinos have become extinct

Answer 13

• collision of a giant asteroid caused huge fires, earthquakes, landslides and tsunamis, the dust that rose masked the Sun, causing low temp and darkness
• plants could not grow

Question 14

give an idea relating to sea ice melting as to why dinos have become extinct

Answer 14

• extinction was a slower process due to the sea ice melting and cooling the sea temperature by about 9 degrees. - less plankton meant less food available.

Question 15

timeline of extinction

Answer 15

origin of life: 3500 mil yrs ago
60% species lost: 440 mil
70% species lost: 360-75 mil
80-95% marine species lost: 251 mil
80% land quadrupeds lost, 50% marine invertibrates lost: 205 mil
50-70% species lost, dinos died out: 65 mil yrs ago

Question 16

why can a mutated pathogen spread rapidly?

Answer 16

• people are immune to it
• no effective treatment

Question 17

how does antibiotic-resistant bacteria get out of control?

Answer 17

• mutations produce new strains, some resistant to antinbiotics
• antibiotics kill individual pathogens that have not developed resistance
• resistant pathogens survive and reproduce and a whole population of a resistant strain develops. this is natural selection.

Question 18

how is rate of development of resistant strains slowed down?

Answer 18

• antibiotics should not be used for mild infections
• correct antibiotics must be prescribed
• patients should always complete each course of antibiotics

Question 19

how does natural selection cause resistant populations of bacteria to develop?

Answer 19

when bacteria are initially exposed to an antibiotic, those most susceptible to the antibiotic will die quickly, leaving any surviving bacteria to pass on their resistant features to succeeding generations.

Question 20

define classification

Answer 20

grouping organisms

Question 21

why is classification useful?

Answer 21

scientists can make more sense of how closely they are related

Question 22

who created the first traditional system of classification?

Answer 22

Carl Linnaeus created the natural classification system

Question 23

how did Linnaeus classify organisms?

Answer 23

into kingdom, phylum, class, order, family, genus and species.

Question 24

how many kingdoms did linnaeus have?

Answer 24

two - plants and animals

Question 25

define the term ‘species’

Answer 25

• smallest group in classification system
• members are very similar and can breed together to produce fertile offspring

Question 26

define binominal system

Answer 26

• living organisms are given a latin name with two parts that all biologists use
• modern man is homeo sapiens

Question 27

why have new models of classificaation been proposed?

Answer 27

due to evidence from improves microscopy and better knowledge of biochemical process

Question 28

what is the current situation regarding kingdoms?

Answer 28

currently three domains are divided into six kindgdoms

Question 29

definwho introduced a ‘domain’?

Answer 29

Carl Woese

Question 30

what evidence was used to find a higher level of classification?

Answer 30

evidence from biochemistry of ribosomes and the way cells divide

Question 31

name the three domains

Answer 31

archaea, bacteria and eukaryota

Question 32

define archaea

Answer 32

primitive form of bacteria, including extremophiles that can live in extreme conditions
- domain has one kingdom: the archaebacteria

Question 33

define the domain bacteria

Answer 33

contains true bacteria as well as cyanobacteria, which can photosynthesise
- domain has one kingdom: the eubacteria

Question 34

define the eukaryota

Answer 34

all have their cells that contain a nucleus enclosing a genetic material.
- domain has four kingdoms: protista, fungi, plants and animals

Question 35

define evolutionary trees

Answer 35

models that can be drawn to she the relationships between different groups of organisms
- when new evidence is found, these evolutionary relationships are modified
- ecological relationships tell us how species have evolved together in an evironment