Biology – the study of lif e

Objectives  Define biology.  Describe the seven characteristics of life.  Name and describe the 3 domains and 6 kingdoms of life

What is Biology? Greek (and Latin) root words: bios = life & logos = study, so.. Biology means the study of the living world and its organisms. An organism is any living thing. Greek philosopher to Medieval alchemist to Charles Darwin

The seven characteristics of life 1)All life is made of cells - life has order; most basic. 2)Reproduction - life comes from life (biogenesis). 3) DNA directs heredity - growth & development. 4) Metabolism transforms energy - energy utilization. 5) Homeostasis - maintenance of steady-state conditions. 6)Response to stimuli - organisms sense and react to their environment. 7) Evolutionary adaptation - life evolves in response to interactions between organisms and environment.

All life is made of cells Cell theory: Φ All organisms are composed of one or more cells; Φ Cells are the smallest units of life; Φ All cells come from pre-existing cells. Two types of cellular organization: 1) Prokaryotic cells ∙ No membrane-bound organelles ∙ DNA is not separated from cytoplasm (no nucleus) ∙ Usually very small in size ∙ Describe unicellular bacteria

All life is made of cells Prokaryotes Usually very small in size (~1 μm*). * 1 micrometer = 1 millionth of a meter (Bacteria on a pinhead)

All life is made of cells 2) Eukaryotic cells Φ Found in protists, fungi, plants, & animals. Φ Subdivided by internal membranes into compartments called organelles. Φ DNA is segregated inside a nucleus. Φ times bigger than prokaryotes. Φ Unicellular & multicellular forms

All life is made of cells Although cells can be seen with a light micro- scope, viruses are too small to be seen that way. (Viruses are not alive – not made of cells.)

All life is made of cells A comparison of sizes

Reproduction Necessary for survival of every species Φ Sexual reproduction - requires 2 cells from different individuals. →→ ex. egg + sperm (offspring are different from parents) Φ Asexual reproduction - a single organism reproduces alone. ex. budding of yeast or splitting of bacteria (offspring are identical to the parent).

DNA directs heredity Life contains genetic infor- mation in the form of DNA (deoxyribonucleic acid). Φ This information is passed from parent to child and is responsible for all charac- teristics such as hair color, eye color, body structure, etc.

Metabolism transforms energy Life uses energy for growth and maintenance. Φ Def: total sum of all chemical reactions in the body. ex. Respiration and photosynthesis CO 2 + H 2 O → C 6 H 12 O 6 + O 2 : ( Carbon dioxide + water → glucose + oxygen )

Homeostasis From Greek: meaning “Steady state”. Φ Def: The ability to maintain stable internal conditions, such as body temperature: perspire to cool & shiver to warm. Blood capillaries in our skin and muscles can be opened or closed to con- serve or lose heat.

Response to stimuli Organisms must respond to danger, hunger, cues for reproduction, etc. Φ Single-celled creatures move toward the food. Φ Plants grow toward the light. Φ Animals sense pain.

Evolutionary adaptation Creatures must “change over time” as the Earth’s environ- ment changes, or they will die out. Φ Charles Darwin wrote of this in his book, On the Origin of Species in 1859.

The tree of life The evolution of life on Earth over 4 billion yrs

All life fits into 1 of 3 domains Domains are based on biochemical & genetic differences. 1) Archaea and 2) Bacteria are prokaryotic (all unicellular bacterial life with no nucleus) 3) Eukarya is eukaryotic (uni- and multicellular organisms with a nucleus. Animals

Within domains, life fits into 1 of 6 kingdoms

The 6 kingdoms of life 2 kingdoms for prokaryotes (all unicellular) are distinguished by habitat in general. ∙ Archaebacteria (archae = ancient) Domain Archaea Live in extreme environments similar to early earth: hot springs, salty seas; oxygen is poisonous. ∙ Eubacteria Domain Bacteria Live all around us: on the floor, in our mouths, on our skin, etc.

The 6 kingdoms of life 3 of 4 kingdoms of multicellular eukaryotes are distinguished, in part by nutrition. ∙ Plants are autotrophic (make food by photosynthesis). ∙ Most fungi are decomposers; they digest food outside their bodies then absorb it. ∙ Most animals digest food within specialized cavities. All other eukaryotes comprise a group called protists. ∙ All but seaweeds are unicellular (ex: amoeba).