Biology (4.3): Classification and Evolution

Binomial system

Binomial system

a system that uses the genus name and the species name to avoid confusion when naming organisms

classification

Arranging organisms into hierarchical groups based upon physical similarities and shared ancestry and evolutionary history

Classification hierarchy (8)

1. Domain

2. Kingdom

3. Phylum

4. Class

5. Order

6. Family

7. Genus

8. Species

Domain

highest taxonomic rank

What are the three domains? (3)

1. Archaea

2. Eubacteria

3. Eukaryotae

Who devised the first classification system in 1735?

Carl Linnaeus

What are the five kingdoms? (5)

1. Plantae

2. Animalia

3. Fungi

4. Protoctista

5. Prokaryotae

What kind of hierarchy is classification?

non-overlapping

Phylum

contains all the groups of organisms that have the same body plan

Class

a group of organisms that all possess the same general traits

Order

a subdivision of the class using additional information about the organisms (e.g. mammal divided into carnivora and herbivora)

Family

a group of closely related genera

Genus

a group of closely related species

species

the basic unit of classification

Biological species

a group of similar organisms that can reproduce to produce fertile offspring

Phylogenetic definition of a species

a group of individual organisms that are very similar in appearance, anatomy, physiology, biochemistry and genetics

Characteristics of prokaryotae (6)

1. no nucleus

2. loop of DNA

3. no membrane-bound organelles

4. small ribosomes

5. smaller cells than eukaryotes

6. free-living or parasitic

Characteristics of protoctista (6)

1. eukaryotic

2. mostly single-celled

3. wide variety of forms

4. show plant-like or animal-like features

5. mostly free-living

6. autotrophic or heterotrophic nutrition

Characteristics of fungi (5)

1. eukaryotic

2. can exist as single cells, or have mycelium with hyphae

3. chitin walls

4. multinucleate cytoplasm

5. free-living and saprophytic

Characteristics of plantae (5)

1. eukaryotic

2. multicellular

3. cellulose cell wall

4. autotrophic

5. chlorophyll

Characteristics of animalia (4)

1. eukaryotic

2. multicellular

3. heterotrophic

4. able to move around

What is used as evidence in classification? (2)

1. comparative DNA sequencing

2. comparative protein analysis

What biological molecules are compared in classification? (2)

1. Cytochrome c

2. DNA

What conclusion can be made if the cytochrome c from two different species is similar?

the two species are closely related

What is cytochrome c used in?

respiration

What does a similar sequence of DNA in two different species mean?

They are more closely related

Who developed the 3 domain classification system in 1977?

Carl Woese

Simple classification (2)

1. limited observational data

2. stable

Using phylogenetic information to classify (3)

1. genet

phylogeny

the study of the evolutionary relationships between organisms

natural selection

the term used to explain how features of the environment apply a selective force on the reproduction of individuals in a population

Who provided evidence for natural selection?

Charles Darwin and Alfred Russel Wallace

What were Darwin’s observations? (3)

1. Overproduction of offspring but population sizes remain constant

2. individuals of a species are not identical

3. offspring are similar to their parents

What were Darwin’s conclusions? (3)

1. Organisms survive more if they have the most useful adaptations

2. Over time these beneficial characteristics become more common

3. Over time many changes can result in new species forming

What are the main evidences for evolution by natural selection? (5)

1. Fossil record

2. DNA and protein analysis

3. homologous features

4. vestigial structures

5. direct observation

How do fossils provide evidence for evolution by natural selection? (2)

1. show extinct organisms from millions of years ago were often simpler

2. organisms appear to increase in complexity as natural selection favours those with better adaptations

How does DNA and protein analysis provide evidence for evolution by natural selection?

shows that there are similarities between biological molecules in different species (e.g. cytochrome c and haemoglobin)

How do homologous features provide evidence for evolution by natural selection?

show that different species have similar anatomical structures

vestigial structures

structures present that are diminished versions of necessary features in their ancestors

Examples of vestigial structures (3)

1. wings of flightless birds

2. tailbones in humans

3. digits and pelvic bones in whales

Interspecific variation

variations seen between individuals of different species

Intraspecific variation

variations seen within populations of the same species

genetic variation

variation caused by possessing a different combination of alleles

environmental variation

variation caused by response to environmental factors

continuous variation

a range of variation between two extreme types

discontinuous variation

where there are distinct categories and nothing in between

What is continuous variation usually as a result of?

many genes and environmental influence

Examples of continuous variation (4)

1. height in humans

2. length of leaves on trees

3. length of stalk of a toadstool

4. number of flagella on a bacterium

Examples of discontinuous variation (2)

1. gender

2. blood groups

What is discontinuous variation usually as a result of?

by only one or two genes and no environmental influence

What kind of graph is used to illustrate continuous variation?

histogram

What kind of graph is used to illustrate discontinuous variation?

bar chart

What are the two general causes of variation?

genetics and the environment

What are the three types of statistical tests? (3)

1. unpaired student’s t-test

2. paired student’s t-test

3. spearman’s rank

correlation coefficient

a measure of how closely two sets of data are correlated

Standard deviation

a measure of the spread around a mean

Student’s t-test

a test used to compare two means

What does a low standard deviation indicate?

data has a narrow range and points are closely grouped to the mean which indicates a greater reliability

What does a high standard deviation indicate

data has a larger range and are less well grouped which indicates a lower reliability

What is the null hypothesis for a Student’s t-test?

there is no significant difference between the means

degrees of freedom =

sample size - the number of data sets

In a student t-test, when is the difference between the two sets of data significant?

when the calculated value of t is lower than the 5% value

Spearman’s rank

uses correlation coefficients to assess the significance of correlations between pairs of data

Using Spearman’s rank, when is there significant correlation?

when the calculated value of Rs is higher than the critical value

In Spearman’s rank, what is Rs?

The rank coefficient

In Spearman’s rank, what is D?

the difference between the ranks

In Spearman’s rank, what is n?

the number of pairs of values

adaptation

a characteristic that enhances survival in a habitat

What are the four types of adaptation?

behavioural, anatomical, biochemical and physiological

Examples of organisms with adaptations (4)

1. marram grass

2. cactus

3. water lilies

4. moles (marsupial vs placental)

Marram grass adaptations (3)

1. thicker wax cuticle

2. sunken stomata

3. leaves roll up

Why is marram grass covered in a thicker wax cuticle?

reduce evaporation

Why does marram grass have stomata sunken into pits?

trap water vapour around stomata and reduce transpiration

Why do the leaves of marram grass roll up?

trap water vapour around the stomata and reduce transpiration

Cactus adaptations (3)

1. spines

2. pleats

3. deep roots

Why do cacti have spines?

decrease SA:V and reduce transpiration

Why do cacti have pleats?

they expand as fleshy tissue fills with water

Why do cacti have deep roots?

to get water from water table

Water lily adaptations (2)

1. stomata on upper epidermis

2. large air pockets within spongy mesophyll

anatomical adaptations

structural features

behavioural adaptations

the ways that behaviour is modified for survival

physiological adaptations

affect the way that processes work

Adaptations of moles (7)

1. cylindrical body

2. small eyes

3. strong front legs

4. large claws on front legs

5. short fur

6. short tail

7. nose with tough skin for protection

What are the two types of moles?

marsupial and placental

Convergent evolution

common features between species in different taxonomic groups

What does convergent evolution occur as a result of?

similar habitats leading to similar selection pressures so natural selection occurs similarly

Examples of evolution by natural selection (4)

1. rat resistance to warfarin

2. head lice resistance to pesticides

3. bacterial resistance to antibiotics

4. human birthweight

Stages of natural selection

1. mutation creates alternative versions of genes

2. genetic variation created between individuals in a species

3. environment selects variations that are advantageous

4. individuals with advantageous characteristics survive and reproduce

5. advantageous characteristics passed on

6. next generation have higher proportion of successful characteristics

What type of variation is important for evolution?

genetic