BIOL120: Chapter 1 (The Study of Life)

all living organisms share 5 fundamental characteristics

1. cells: made up of membrane-bound cells

2. replication: capable of reproduction

3. information: process hereditary information encoded in genes as well as information from the environment

4. energy: acquire and use energy

5. evolution: populations of organisms are continually evolving

cell theory

what are organisms made of?

life characteristic 1: all organisms are made of cells

life characteristic 2: all cells come from preexisting cells

theory of evolution

where do organisms come from?

life characteristic 5

chromosomal theory of inheritance

how is hereditary information transmitted from one generation to the next?

life characteristics 3 and 4: hereditary or genetic information is encoded in genes—units located on chromosomes

cell

a highly organized compartment bound by plasma membrane, containing concentrated chemicals in an aqueous solution

spontaneous generation

obsolete theory suggesting living organisms arise from inanimate objects

redi’s experiment

francesco redi disproved the theory of spontaneous generation in the 1600s by using a sealed jar as the control to show that flys does not come from the meat itself

louis pasteur’s hypothesis

cells arise from cells, not by spontaneous generation

experiment done with a straight-necked flask (where cells appear in flask after preexisting cells enter flask from air) and a swan-necked flask (where no cells appear in flask as preexisting cells from air are trapped in swan neck)

couldn’t just seal the flask because opponents argued that air was vital for spontaneous generation

james watson and fracis crick

proposed that dna is a double-stranded helix and won the nobel prize in 1962

dna

carries or encodes information needed for an organism’s growth and reproduction

made of double helix, consisting of four building blocks:

• adenine (a), thymine (t), cytosine (c), and guanine (g)

• strands are held together by single or double bonds

• this pairing allows dna to be copied

the central dogma

describes the flow of information in cells

dna → rna → proteins

• dna’s information is transcribed into an rna copy

• the rna copy is translated to determine what building blocks to use to make a protein

protein’s determine physical traits

natural selection

explains how evolution occurs

two conditions must be met in a population:

• individuals must vary in characteristics that are heritable

• in a particular environment, certain versions of these heritable traits help individuals reproduce more than other versions (i.e. adaptations)

fitness and adaptation drive natural selection

fitness

the ability of an individual to produce offspring

adaptation

a trait that increases the fitness of an individual in a particular environment

speciation

occurs when populations diverge to form new species

tree of life

a family tree of organisms that describes the genealogical relationships among species with a single ancestral species at its base

phylogeny

is the actual genealogical relationships among organisms

Biologists study rna and dna from different organisms

• compare sequences of the building blocks (a,t,c,g)

• fewer sequence variations between two species may indicate a closer relationship

phylogenetic trees

used to show the relationships between species

the more recently species share a common ancestor, the more closely related they are

taxonomy

the effort to name and classify organisms

taxon is a named group

binomial nomenclature

Genus species

genus

made up of a closely related group of species

species

made up of individuals

• that regularly breed together

• whose characteristics are distinct from those of other species