Cell Theory and Evolutionary Biology

Basic properties of cells

Organized and complex, use energy, respond to stimuli, reproduce, and evolve

Cells use energy for

chemical work, mechanical work, transport (osmotic) work

A mammalian red blood cell has no DNA and cannot reproduce. Is it alive?

Alive

Modern Cell Theory

1. All living organisms are made of one or more cells

2. The cell is the structural and functional unit of life

3. All cells arise from a pre-existing cell, by division

All cells arise from a pre-existing cell, by division

All cells contain hereditary in the form of DNA

All cells are basically the same in biochemical composition

Universal genetic code, shared fundamental metabolic pathways, same basic architecture for protein-making molecular machinery

All cells are ___ and must have a ___ ___.

related, common origin

The proximity of organisms on a phylogenic tree reflects ___ of characteristics (genetic distance)

similarity

Organisms from common branches have ___ characteristics

shared

In many phylogenetic trees, but not all trees, the length of branches reflects ___ ___.

Genetic distance

Biologists recognize two types of cells

Prokaryotes and eukaryotes

Prokaryotes

• No nuclei

• No membranous organelles

• Simple genome (a circular molecule of DNA)

• Smaller size

• Sterols usually absent from membranes (cell walls)

Eukaryotes

• Nucleated

• Membranous organelles

• Several DNA molecules (chromosomes, linear)

• Bigger size

• Sterols in membranes

Prokaryote domains

Bacteria and archaea

Eukaryote domains

eukarya (animals, plants, fungi, protists)

Prokaryote unicellular vs multicellular

always unicellular

Eukaryote unicellular vs multicellular

unicellular or multicellular

Prokaryote size

Smaller (1-5 mM)

Eukaryote size

Larger (10-100 mM)

Prokaryote DNA location

nucleoid region (free floating)

Eukaryote (DNA location)

Stored in nucleus

Prokaryote DNA form

circular (plasmids)

Eukaryote DNA form

Linear (chromosomes)

What did the last universal common ancestor (LUCA) look like?

Small, single-celled “prokaryote-like”

Had a cell wall and/or a membrane

Followed the central dogma of molecular biology

RNA molecules (tRNA, rRNA) provided critical analytic activity

Although derived from a single fertilized egg cell, the human body is comprised of about ___ cells

10¹³

Biological diversity between different organisms

Evolution accounts for both the diversity and unity in life on Earth

All living organisms use the same biochemical toolkit

Individual species have unique DNA sequences (genomes)

Differences in genes create lineage-specific gains, losses, and modifications

Differ in gene expression

Biological diversity within organisms

Every cell within an organism contains an identical genome

Cell differentiation: stem cells become specialized

Differential Gene Expression: only certain genes are active in each cell type

Functional diversity

Gene expression and protein synthesis

determine:

• Cell shape

• Cell function

• Complex behavior

Gene expression =

Information flow

Gene

DNA sequence that encodes a RNA/protein product