BABS1201 Lecture Notes - Lecture 1: Carbon, Elements Of Life, Protist
17 May 2018
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BABS1201
2ND MARCH 2018
CELLS, PART I
LIST THE MAJOR ELEMENTS OF LIFE – (CHAPTER 2, CONCEPT 2.1)
× Most abundant elements in universe: Hydrogen (H), Helium (He), Oxygen (O), Carbon (C)
× Major elements of life: Carbon (C), Hydrogen (H) Phosphorus (P), Oxygen (O), Nitrogen (N),
Sulfur (S) ® these elements are present in quite uniform relative amounts across
organisms- C, H, O in carbohydrates; N, P in DNA and S in some amino acids (cysteine)
× These ‘molecules of life’ are quite different to the most abundant elements in the universe
EXPLAIN HOW THE DIVERSITY OF LIFE IS CLASSIFIED – (CHAPTER 1, CONCEPT 1.2)
× Life is diverse- diversity is a hallmark of life
× Biologists have identified around 1.8 million species, but estimates of the number of
species on earth vary from 10-100 million
- Classification- initially, this was done by examining structures, functions and other
obvious features
- Currently, nucleic acid comparisons are used, rather than structural comparison
e.g. 16s (a particular ribosomal subunit) rRNA in bacteria is compared between
organisms as it is ‘quite conserved’
× In bacteria, they have this gene, as well as in most eukaryotes (in their
mitochondrial genome)- by comparing the similarity of that DNA sequence,
we can start to draw phylogenetic trees and determine the relatedness
between these organisms
- Scientists have classified life into species and broader classifications- each species
has a two-part name (i.e. in the format Genus species, like Staphylococcus aureus)
- At the highest level, life is classified into three domains- Bacteria, Archaea,
Eukarya (including the plant, fungi and animal kingdoms, and the protists)
- Bacteria and archaea are commonly termed as prokaryotes (a loose definition,
“informal classification” of these two microbial domains)- these cell types share a
general cell structure
- Protista- also an informal term- unicellular organisms which are classified under
eukaryotes but do not really share any similarities with plants, fungi or animals-
most numerous and diverse eukaryotes
