4.3 - classification

classification

the process of organising organisms into groups based on their similarities

taxonomic system

1. domain

2. kingdom

3. phylum

4. class

5. order

6. family

7. genus

8. species

three domains

• bacteria

• archaea

• eukarya

four kingdoms in eukarya

• plantae

• animalia

• protoctista

• fungi

how binomial names are written

• genus - first letter uppercase

• species - all lowercase

cell type of five kingdoms

• plant - eukaryotic

• animal - eukaryotic

• prokaryotae - prokaryotic

• protoctista - eukaryotic

• fungi - eukaryotic

cellular organisation of five kingdoms

• plant - multicellular

• animal - multicellular

• prokaryotae - unicellular

• protoctista - unicellular

• fungi - unicellular or multicellular with body made of hyphae

nucleus plant of five kingdoms

• plant - present

• animal - present

• prokaryotae - no nucleus

• protoctista - present sometimes

• fungi - present

cell walls of five kingdoms

• plant - yes

• animal - no

• prokaryotae - yes, often made of peptidoglycan

• protoctista - variable

• fungi - yes, made of chitin

nutrition of five kingdoms

• plant - autotrophic

• animal - heterotrophic

• prokaryotae - either or parasitic

• protoctista - either or parasitic

• fungi - saprophytic

reproduction of five kingdoms

• plant - seeds or spores

• animal - variable

• prokaryotae - binary fission

• protoctista - variable

• fungi - spores

storage of sugars of five kingdoms

• plant -starch

• animal - glycogen

• prokaryotae - glycogen

• protoctista - variable

• fungi - glycogen

Domain bacteria

• Contains the kingdom Eubacteria only, found in all environments.

• Prokaryotic unicellular organisms.

• Distinct cell membrane lipids.

• Have peptidogylcan (murein) in their cell walls.

Domain Archaea

• Contains the kingdom Archaebacteria only, typically found in extreme environments.

• Prokaryotic unicellular organisms.

• Have histones so gene and protein synthesis is more similar to Eukarya than Bacteria.

• No peptidogylcan in their cell walls.

Domain Eukarya

• Contains four kingdoms from the five kingdom system: Animalia, Plantae, Fungi, Protoctista.

• All have nuclei and membrane-bound organelles.

Phylogenetic classification

classification based on evolutionary relationships between organisms and their ancestors, classifying species into groups. It reveals how closely related organisms are.

advantages of phylogenetic classification

• It produces a continuous tree that doesn't force organisms into specific taxonomic groups where they don't quite fit.

• There is no overlap between the groups produced.

what does phylogeny indicate?

lines of descent and divergence over time

what does modern taxonomy use to determine phylogeny

• Comparisons between DNA and amino acids in proteins

• Comparisons of embryonic similarities and differences.

• Comparisons of similarities in species' physical characteristics e.g. from fossils.

• Comparisons of similarities and differences between the behaviour of species.

Palaeontology

the study of life's history as recorded in fossils

key evidence from fossils that support evolution

• Simple bacteria and algae fossils are found in the oldest rocks, progressing to more complex vertebrates in newer rocks.

• Plant fossils appear before those of animals that feed on these plants, indicating a natural order of evolution.

why are fossil records incomplete?

• Many organisms decompose before they can fossilise.

• Over time, many fossils have been lost due to erosion or geological processes.

• Many organisms have not yet been discovered.

homologous structures

physical features in different species that have a similar underlying structure but may serve different functions

Comparative biochemistry

involves studying the molecular aspects of organisms to uncover evolutionary relationships

useful molecules to study evolutionary links

• Ribosomal RNA - integral to protein synthesis so it changes slowly, making it useful for showing connections between species that diverged long ago.

• Nuclear, mitochondrial, or chloroplast DNA - Species that are more closely related will have more similar DNA sequences.

• Messenger RNA - Base sequences of mRNA are complementary to DNA so can assess DNA diversity.

• Amino acids - If they are closely related evolutionarily, two species have more similar amino acid sequences because they are determined by mRNA and DNA.

The hypothesis of neutral evolution

explains how much genetic change happens not because it is beneficial, but simply by chance

Variation

the differences observed among individuals within any given population

Sources of genetic variation

• Mutations - Changes to genes and chromosomes that may be passed on to the next generation

• Meiosis - New combinations of alleles are present in the gametes formed, produced by independent assortment of chromosomes and crossing over between chromatids

• Random fertilisation - Random fertilisation of gametes produces new combinations of alleles in a zygote

• Random mating

environmental factors that can cause variation

1. Light

2. Nutrient and food availability

3. Temperature

4. Rainfall

5. Soil conditions

6. pH

polygenes

• genes at different loci that all contribute to a particular aspect of phenotype

continuous variation

when there are a range of values between two extremes without distinct categories, which produce a spectrum of phenotypes

discontinuous variation

• features clear, distinct categories with no intermediates

• e.g. human blood types can be classified as A, B, AB, or O

Intraspecific variation

variations that occur within a species

Interspecific variation

variations that occur between different species

what does a smaller SD indicate?

here are fairly consistent values that are clustered around the mean

what does a larger SD indicate?

There are fairly inconsistent values that are widely spread around the mean

what are student t-tests used for

to determine if there is a significant difference between the mean values of a particular variable across two populations

conditions for using student's t-test are

• The data must be continuous and normally distributed.

• The variances of the populations should be equal.

• The samples must be independent of each other.

Correlation

the relationship between two variables

what is used to assess correlation

Spearman’s rank

adaptation categories

• Anatomical - Physical structures, both internal and external

• Behavioural - Activities and responses, whether inherited or learned

• Physiological - Internal biological functions
  

selection pressures

environmental factors that affect their survival and reproduction

selection pressures examples

• Predation

• Competition for resources

• Climate change

• Disease

genetic diversity

the total number of different alleles in a population

how does genetic diversity influence natural selection

organisms with advantageous traits are more likely to survive, reproduce, and pass on their alleles, influencing the gene pool

process of natural selection

1. There is variation in characteristics within a species.

2. More genetic variation emerges within a population due to random mutations.

3. Individuals with alleles that code for advantageous traits for survival are more likely to reproduce

4. These advantageous alleles are passed down to offspring

5. Over time, these beneficial alleles become more common in the population.