Unifying Themes in Biology

Unifying Themes In Biology

Biology encompasses a vast amount of information, necessitating a focus on unifying themes to aid understanding.
Key unifying themes:
- Organization
- Information
- Energy and matter
- Interactions
- Evolution

Organization

Organization is a key unifying theme in biology.
Levels of Biological Organization:
- Biosphere
- Ecosystems
- Communities
- Populations
- Organisms
- Organs
- Tissues
- Cells
- Organelles
- Molecules
Emergent Properties vs. Reductionism
- Emergent properties:
  - Result from the arrangement and interaction of parts within a system.
  - Novel properties emerge at each level of biological organization.
  - Complexity increases with each level due to arrangements and interactions.
- Reductionism:
  - Involves studying the interactions that underlie emergent properties of a system.
  - Used to study life at all levels.
Structure and Function
- Correlation between structure and function at each level of biological organization.
- Example: Microvilli in the small intestine (tissue level).
- Example: Musculoskeletal system differences between cheetahs and lions.
The Cell
- The cell is the basic unit of life.
- All cells share certain characteristics (e.g., membrane).
- Two main forms of cells:
  - Prokaryotic
  - Eukaryotic

The Cell

Eukaryotic Cell
- Contains membrane-enclosed organelles.
- Includes a DNA-containing nucleus.
Prokaryotic cells
- Lack a nucleus or other membrane-bound organelles.
- Generally smaller than eukaryotic cells.

Information

Chromosomes contain a eukaryotic cell’s genetic material in the form of DNA (deoxyribonucleic acid).
DNA, Genes, & Chromosomes
- DNA
  - Adenine
  - Cytosine
  - Thymine
  - Guanine
  - Sugar phosphate backbone
- Gene (segment of DNA)
DNA = blueprints for making proteins
DNA (gene) -> RNA -> Protein

Information - DNA

Gene expression = converting gene info into cellular product
Transcription: DNA (part of the crystallin gene) to mRNA
Translation: mRNA to chain of amino acids
Protein folding: Chain of amino acids to Crystallin protein

Information - Transmission

Nuclei containing DNA in sperm and egg cells.
Fertilized egg with DNA from both parents.
Embryo’s cells with copies of inherited DNA.
Offspring with traits inherited from both parents.

Information - Genome

An organism’s genome is its entire “library” of genetic instructions.
Genomics is the study of sets of genes in one or more species.
Proteomics refers to the study of sets of proteins and their properties.
The entire set of proteins expressed by a cell, tissue, or organism is called a proteome.
Genome Size
- E. coli: $4.6$ Mbp, $4,300$ coding genes, $1$ chromosome
- S. cerevisiae: $12$ Mbp, $6,600$ coding genes, $16$ chromosomes
- S. pombe: $13$ Mbp, $4,800$ coding genes, $3$ chromosomes
- D. discoideum: $34$ Mbp, $13,000$ coding genes, $6$ chromosomes
- C. elegans: $100$ Mbp, $20,000$ coding genes, $12$ ( $2n$ ) chromosomes
- D. melanogaster: $140$ Mbp, $14,000$ coding genes, $8$ ( $2n$ ) chromosomes
- A. thaliana: $140$ Mbp, $27,000$ coding genes, $10$ ( $2n$ ) chromosomes
- P. patens: $510$ Mbp, $28,000$ coding genes, $27$ chromosomes
- M. musculus: $2.8$ Gbp, $20,000$ coding genes, $40$ ( $2n$ ) chromosomes
- H. sapiens: $3.2$ Gbp, $21,000$ coding genes, $46$ ( $2n$ ) chromosomes

Genes and Alleles

Allele: Brown and Blue
Locus for eye color gene
pair of chromosomes

Genotype vs Phenotype

Genotype
Phenotype

Energy and Matter

Life Requires the Transfer and Transformation of Energy and Matter

ENERGY FLOW

Light energy comes from the sun.
Plants convert sunlight to chemical energy.
Organisms use chemical energy to do work.
Heat is lost from the ecosystem.
Chemicals in Plants are passed to organisms that eat the plants.
Plants take up Chemicals from the soil and air.
Decomposers such as fungi and bacteria break down leaf litter and dead organisms, returning chemicals to the soil.

Energy and Matter – Summary

Input of energy, mainly from the sun, and transformation of energy from one form to another make life possible.
Plants and other photosynthetic organisms (producers) convert the energy of sunlight into the chemical energy of sugars.
This chemical energy of these producers is then passed to consumers that feed on other organisms or their remains.
Energy flows through an ecosystem, generally entering as light and exiting as heat.
Matter cycles within an ecosystem, where it is used and recycled.
Chemical elements are taken up by plants, can be passed to animals that eat the plants, and are eventually returned to the environment by decomposers.

Interactions

Every organism interacts with other organisms and with physical factors in its environment.
Organism-Organism Interactions:
- Mutualism: +/+
- Commensalism: +/0
- Parasitism: +/-
- Predation: +/-
- Competition: +/- or -/-

Interactions: Organisms-Environment

Impacts of organism on environment
- Human pollutants and emissions
- Climate change
- Extreme weather events
- Shifting wind and precipitation patterns
- In turn, impacts organisms living in those environments
Impacts of environment on organism
- Higher risk of drought conditions leaves amphibian populations at risk

Evolution

Evolution accounts for the unity and diversity of life.
Evolution is a process of biological change in which species accumulate differences from their ancestors.
Differences between two species indicate that heritable changes occurred after divergence from a common ancestor.
Similar traits in two species are explained by descent from a common ancestor.
Scientific explanation for the unity and diversity of organisms

Evolution – Classifying Diversity

Humans group diverse items according to their similarities and relationships to each other.
Careful comparison of form and function has been used to classify life-forms.
New methods of assessing species relationships, especially comparisons of DNA sequences, have led to a reevaluation of larger groupings.

Evolution - Classifying the Diversity of Life

3 Domains
- Bacteria
- Archaea
- Eukarya

Domains - Eukarya

Domain Eukarya includes all eukaryotic organisms
Domain Eukarya includes three multicellular kingdoms: Plantae, Fungi, and Animalia
Plants produce their own food by photosynthesis
Fungi absorb nutrients from their surroundings
Animals obtain food by eating and digesting other organisms

Evolution: Unity in Diversity of Life

Genetic Code
Body Plan
Homologous Structures

HOX Genes

responsible for body plan
Conserved throughout the animal kingdom

Charles Darwin and the Theory of Natural Selection

Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859
Darwin made two main points
- Species showed evidence of “descent with modification” from common ancestors
- Natural selection is the primary cause of descent with modification
Darwin’s theory captured the duality of life’s unity and diversity

Charles Darwin and the Theory of Natural Selection

Darwin’s Observations
- Individuals in a population vary in their traits, many of which are heritable
- More offspring are produced than those survive, and competition is inevitable
- Species generally are suited to their environment
Darwin’s reasoning
- Individuals that are best suited to their environment are more likely to survive and reproduce

Natural Selection

Population with varied inherited traits
Elimination of individuals with certain traits that make them more visible
Reproduction of survivors
Increased frequency of traits that enhance survival

Natural Selection

Mechanism of evolutionary adaptation
Natural environment “selects” for advantageous traits in the population
Brings about adaptive evolution by acting on an organism’s phenotype

Evolution and Natural Selection in Medicine

Bird flu is continuing to spread in animals across the US.
So far, 70 human cases have been confirmed, according to the CDC.

Adaptive Evolution

Adaptive evolution is a continuous, dynamic process

Unifying Themes Appear in Development

ONTOGENY
- FERTILIZED EGG
- LATE CLEAVAGE
- BODY SEGMENTS
- LIMB BUD STAGE
- LARVA/FETUS
- ADULT/OFFSPRING