4.2.2 Classification and Evolution

Question 1

why do scientists classify organisms?

Answer 1

to identify species
to predict characteristics
to find evolutionary links

Question 2

identifying species

Answer 2

by using a clearly defined system of classification, the species an organism belongs to can be easily identified, e.g based on physical & molecular similarities

Question 3

predicting characteristics

Answer 3

if several members of a group have similar characteristics (anatomical, physiological, behavioural) it is likely they belong to the same/similar taxonomic group

Question 4

finding evolutionary links

Answer 4

species in the same taxonomic group will likely share characteristics as they will have descended from the same common ancestor

Question 5

taxonomy

Answer 5

naming + grouping species within a ranking system
organisms are grouped into taxa (a taxon)

Question 6

biological classification

Answer 6

organising both living and extinct species into systematic groups
based on DNA sequence (genome) and physical characteristics

Question 7

hierarchical classification

Answer 7

group similar organisms together
species = lowest taxonomic rank
domains = highest taxonomic rank

Question 8

advantages of binomial naming system

Answer 8

universal language
useful in predicting characteristics
allows us to distinguish between some species within the same genus which are similar

Question 9

definition of a species

Answer 9

group of organisms with similar morphological and physiological features that can breed together and produce fertile offspring.

Question 10

suggest why the defintion of a species does not include all organisms and may lack accuracy

Answer 10

does not account for asexually reproducing organisms
members of the same species may have low sperm counts/low-quality sperm or eggs
no account for genetic diversity in species

Question 11

prokaryotae

Answer 11

unicellular
murein cell walls
autotrophic, saprotrophic nutrition
flagella for motility
e.g E.coli

Question 12

protoctista

Answer 12

single-celled
nuclear envelopes
sometimes vacuoles & cell walls
heterotrophic, autotrophic nutrition
cilia & flagella for motility
no nervous co-ordination
e.g. Amoeba

Question 13

fungi

Answer 13

multi or unicellular
nuclear envelopes
chitin cell walls
sometimes have vacuoles
saprotrophic nutrition
e.g. uni = yeast
multi = mushrooms

Question 14

plantae

Answer 14

multicellular
nuclear envelopes
cellulose cell walls
vacuoles surrounded by a tonoplast
many membrane-bound organelles
photoautotrophic nutrition
e.g. rose

Question 15

taxonomic ranks

Answer 15

domain - do
kingdom - king
phylum - prawns
class - cook
orders - oysters
family - for
genus - giant
species - squid

Question 16

Animalia

Answer 16

multicellular
nuclear envelopes
no cell walls
heterotrophic nutrition
nervous co-ordination
e.g. humans

Question 17

archaea

Answer 17

prokaryotae split into bacteria and archaea
extremophiles - tend to live in extreme environments
more complex RNA polymerase
more stable plasma membrane

Question 18

autotrophic

Answer 18

organisms which use carbon dioxide and water (inorganic molecules) to synthesise organic compounds

Question 19

photoautotrophic

Answer 19

obtain nutrition through photosynthesis

Question 20

chemoautotrophic

Answer 20

obtain their nutrition through inorganic
molecules e.g. sulfur

Question 21

heterotrophic

Answer 21

organisms which feed on organic compounds produced by other organisms

Question 22

saprotrophic

Answer 22

organisms which secrete enzymes, externally digest food substances and then absorb the products of digestion into the organism e.g. fungi.

Question 23

bacteria features

Answer 23

unicellular
cell wall of peptidoglycan
very simple cytoskeleton
no membrane-bound organelles - prokaryotic
circular DNA - nucleoid

Question 24

archaea features

Answer 24

unicellular
cell wall of pseudopeptidoglycan
complex cytoskeleton
no membrane-bound organelles - prokaryotic
circular DNA - nucleoid
some introns
histone proteins in combination with DNA

Question 25

eukarya features

Answer 25

unicellular or multicellular
cell wall - not of peptidoglycan
chromosomes in the nucleus
introns
lots of histone proteins in combination with DNA

Question 26

three domains

Answer 26

bacteria (prokaryotes)
archaea (prokaryotes)
eukarya (eukaryotes)

Question 27

key differences between archaea & bacteria

Answer 27

seen in membrane lipids, ribosomal RNA, cell wall composition

Question 28

using DNA sequences in classification

Answer 28

base sequences in regions of DNA are used to establish evolutionary relationships
the more similar the DNA, the more closely related the species

Question 29

phylogeny

Answer 29

the study of evolutionary relationships between different species based on physical traits

Question 30

explain why the structure of a phylogenetic tree may change over time

Answer 30

random mutations may occur - produces new alleles, which may make 2 species more/less closely related
speciation could occur due to isolating mechanisms
new evidence discovered

Question 31

five kingdoms

Answer 31

Prokaryota
Protoctista
Fungi
Plantae
Animalia

Question 32

advantages phylogenetic classification has over traditional hierarchal taxonomic classification

Answer 32

more visual representation
gives time scales and indicates precisely where two species evolved from a common ancestor

Question 33

homologous features

Answer 33

shared by organisms that have evolved from a common ancestor

Question 34

phylogenetic trees

Answer 34

show the evolutionary relationships between different taxa

Question 35

process of natural selection

Answer 35

random mutation
better adapted when selection pressure applied
survive and reproduce = pass on alleles

Question 36

hybrid

Answer 36

infertile offspring of 2 organisms with the same genus, different species

Question 37

what makes archaea good extremophiles

Answer 37

mono-lipid cell membrane is resistant to being disrupted

Question 38

main differences between archaea and eubacteria

Answer 38

archaea = no peptidoglycan in cell wall
different number of proteins in RNA polymerase
A = mono-lipid cell membrane E = bilipid cell membrane
E = found in all environments A = extreme environments

Question 39

use of biological molecules in classification

Answer 39

using DNA sequences: base sequences establish evolutionary relationships - mapped out using phylogeny. DNA can be extracted from fossils. the more similar the DNA, the more closely related
using protein/amino acid sequences: changes in DNA cause changes in protein structure

Question 40

Darwin’s theory

Answer 40

individuals that are better adpated to their environment compete better than others, survive longer and reproduce more, so pass on more of their successful characteristics to the next generation
survival of the fittest
used the analogy of selective breeding to explain natural selection

Question 41

Darwin’s explanation of his theory, using the giraffe’s long neck

Answer 41

a random genetic variation in neck length
in an environment with trees and bushes, long necked animals were better adapted compared to the short necked animals.
these animals lived longer, through more breeding seasons and had more offspring.
in the next generation, there were more long necks than short necks

Question 42

selective breeding

Answer 42

humans choose desirable characteristics and only those individulals, with the best characteristics, are used for breeding
species can then be changed over a long period of time

Question 43

differences between artifical and natural selection

Answer 43

artificial = humans with a goal
natural = nature does not have a goal