Biology: An Overview

bio- =
-logy =
The natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution.

Life Criteria

Organisms are open systems
Maintain homeostasis
Are composed of cells
Have a life cycle
Undergo metabolism
Can grow
Adapt to their environment
Respond to stimuli
Reproduce
Evolve

Biochemsistry

Elements of Life
~99% of all living cells are composed of only six elements—carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus.

Importance of Water for life
Solvent
Temperature buffer
Water is a metabolite
Living Environment

Biochemsistry: Carbon

45-50% of all dry biomass is carbon.
Many important characteristics:
It has four valence bonds
Bonding energy required is at a level for easily building molecules which are stable and reactive.
Carbon atoms bond readily to other carbon atoms.

Biomolecules

Carbohydrates
- Provides for energy storage, genetic information, cell communication, and organism structure.
Lipids
- Water-insoluble or nonpolar compounds
Proteins
- Very large molecules made from amino acids.
- Functions: catalyzing metabolic reactions, DNA replication, and molecule transportation, plus more…
Nucleic acids
- complex, high-molecular-weight macromolecules
- convey genetic information; DNA and RNA

The Cell: Cell Theory

Living organisms are made up of one or more cells.
Cells are the basic structural and organizational unit of all organisms.
All known living cells arise from pre-existing cells by division.
Energy flow (metabolism and biochemistry) occurs within cells.
Cells contain:
- DNA which is found in the chromosomes.
- RNA found in the cell nucleus and cytoplasm.

Prokaryotes

Relatively small cells surrounded by the plasma membrane (cell wall).
Protoplasm (cell content) contains a chromosomal region and cytoplasm.
Lack a nucleus and other membrane- enclosed structures (organelles).
Bacteria and Archaea are the two Domains.

Eukaryotes

Cells surrounded by plasma membrane.
Have distinct nuclei bound by a nuclear membrane.
Contain membrane-bound organelles.
Organized chromosomes which store genetic material.
Domain Eukarya: Plants, Animals, Fungi, etc.

Genetics

Genes are the primary units of inheritance.
- a region of a DNA (Deoxyribonucleic acid) strand that influences organism form or function in specific ways.
Cells transcribe a DNA gene into an RNA (Ribonucleic acid).
- Ribosome (complex molecular machines) translates RNA into a sequence of amino acid proteins.
Chromosome: organized structure consisting of DNA and histones.
- Linear chromosomes in eukaryotes
- Circular chromosomes in prokaryotes.
Genome: set of chromosomes and other hereditary information (mitochondria, chloroplasts).
- Eukaryotes: genomic DNA is localized in cell nucleus, or with small amounts in mitochondria and chloroplasts.
- Prokaryotes: DNA is an irregularly shaped body in cytoplasm called the nucleoid.

Botany: The Study of Plants

Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae.
About 300–315 thousand plants species.
Green plants have cellulose cell walls.
Obtain energy from sunlight via photosynthesis.
Generally characterized by sexual reproduction, but asexual reproduction is also common.
Basis of most of Earth's ecosystems, (especially land).
Major source of basic foodstuffs
Many other uses:

Zoology: The Study of Animals

Multicellular eukaryotic organisms of the kingdom Animalia.
- Characteristics:
- Consume organic material
- Breathe oxygen
- Are able to move
- Reproduce sexually
- Grow from a hollow sphereof cells, the blastula, duringembryonic development.
Over 1.5 million living animal species have been described

Other Important Aspects of Biology

Ecology and Ecosystems - The relationships and processes linking each living thing to the physical and chemical environment.
Evolution - Change through time. All living organisms are evolutionary descendants of life-forms that existed during the past
Biodiversity - Totality of genes, species and ecosystems of a region.

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