Why do we classify organisms (4answers)
- avoid confusion
- learn how organisms are related to eachother
- understand diversity
- trace the evolutionary history of a species
How do we classify organisms?
Bionomial naming.
Order of hierarchical classification (7):
(technically 1 is domain, which is prokayrote or eukaryote) 1. (most inclusive) Kingdom 2. Phylum 3. Class 4. Order 5. Family 6. Genus 7. Species
What do branch points represent in phylogentic trees?
the common ancestor of all the groups after it
What defines a species?
A group of organisms that can interbreed and produce fertile offspring.
What are phylogenetic trees designed to show?
Patterns of descent, NOT phynotypic similarity.
Molecular DNA sequencing to determine phylogenetic relationships initially used what genes? Why?
They initially used genes that encode ribosomes because ribosomes exist in all cells (eukaryotic and prokaryotic) (because all cells need proteins and proteins are synethised by ribosome)
What component is found in bacteria cell walls? and what is it?
Peptidogylcan, protein + sugar
Describe where the genetic material in bacteria is found and what shape it is.
DNA is free floating in the cytoplasm and the chromosome is circular. They can also have plasmids which are small circular bits of DNA.
3 domains based on genome sequencing?
- bacteria
- arcaea
- eukaryotes
4 things that are distinct to prokaryotes?
- mostly unicellular but can be multicellular
- No nucleus, DNA not membrane bound
- no membrane bound organelles
- reproduce by binary fission
2 domains of prokaryotes?
- bacteria
- Archaea
What are bacteria’s 3 common shape and how big are they?
shapes: spheres, rods, spirals
size: 1-5um, about 100x smaller than eukaryotic cells
True of false: DNA can transfer between bacteria
True
Why do bacteria have cell walls?
Protection
What is the difference between gram-positive bacteria and gram negative?
Gram-positive bacteria has the peptidoglycan layer on the otherise of the plasma membrane, whereas gram-negative bacteria have little to no peptidoglycan, which is sandwiched between lipids in their membrane.
Describe the features of prokaryotes that enable them to diversify rapidly and adapt to different environments.
rapid evolution due to small genomic size which allows them to live in a wide range of environments
What is a difference between bacteria and archaea?
archea do NOT have peptidoglycan, and their membrane lipids have branched hydrocarbons
Give an example of a change Archeae makes to the cell in order to survive in extreme environments.
They have modifications in their amino acids which mean they are much more stable and maintain shape in extreme environments.
Name the last known common ancestor of archeae and eukaryotes and why it is important
lokiarchaeum. They have genes that encode cytoskeleton which is the beginning of internal organisation within cells, which is what eukaryotes have.
Provide 3 lines of evidence that support mitochondria and chloroplasts having bacterial origins.
chloroplasts divide by binary fission like bacteria, and mitochondria have their own DNA
What is secondary endosymbiosis?
An evolutionary process when an evolving eukaryotic cell with a mitochondria engulfs a photosynethetic bacteria which enables the cell to use light energy as food
Describe how genes encoding the cytoskeleton could have helped eukaryote evolution
The cytoskeleton may have helped organise the organelles inside the evolving eukaryotic cell such as the nucleus
What is the theory of endosymbiosis
The theory of how prokaryotes evolved into eukaryotes.
