Chapter 1- Tree Of Life Flashcards
Define theory
An explanation for a general class of phenomena or observations
The discovery of the cell
In 1665 Robert Huck use a crude microscope to examine the structure of court from an oak tree. The instrument magnified objects up to 30 times their normal size and allowed him to see something extraordinary, he observed small pore like compartments that were invisible to the naked eye. These became known as cells.
Further observations of the cell
Soon after Hooke, Anton van Leeuwenhoek succeeded in developing much more powerful microscopes, with these instruments he inspected samples of pond water and made the first observation of single-celled organisms like the Paramecium
Smallest organism
Bacteria, which consist of a single cell and are 200 nm wide
Definition of a cell
A highly organized compartment that is bounded by thin flexible structure called a plasma membrane and that contains concentrated chemicals in an aqueous solution
The components of scientific theories
The first describes a pattern in the natural world, while the second identifies a mechanism or process that is responsible for creating that pattern
Who added the process component of the cell theory?
Rudolph Virchow in 1858
The complete cell theory
All organisms are made of cells, and all cells come from pre-existing cells
Define hypothesis
A proposed explanation
Spontaneous generation
The belief that organisms arose spontaneously under certain conditions
The difference between theory and hypothesis
Theories refer to proposed explanations for broad patterns in nature and hypotheses refer to explanations for more tightly focused questions
Prediction
Something that can be measured and that must be correct if the hypothesis is valid
Louis Pasteur’s idea
He wanted to determine whether microorganisms could arise spontaneously in a nutrient broth or whether they appear only when a broth is exposed to a source of pre-existing cells.
Louis Pasteur’s experiment
He created to treatment groups: a broth that was not exposed to a source of pre-existing cells and he brought that was. Both treatments were identical in every respect but one. Both used glass flasks filled with the same amount of nutrient broth and both were boiled for the same amount of time to kill any existing organisms. But one had a straight neck exposed to preexisting cells after sterilization (the straight neck allowed pre-existing cells like bacteria and fungi that cling to dust particles in the air to drop into the nutrient broth) and one had a swan neck (this allowed water to condense in the crook of the neck after boiling and this pool of water would trap any bacteria or fungi that entered in on dust particles, thereby making it isolated from any pre-existing cells).
Pasteur’s results
His data suggested that the spontaneous generation hypothesis was incorrect and that all cells came from pre-existing cells. His experiment was enough to prove to other biologists the validity of this.
Descent with modification
Characteristics of species can be modified from generation to generation
Evolution
- Species are not independent unchanging entities, but are related to one another and can change the time (pattern component)
- Occurs when heritable variation leads to differential success in reproduction
Natural selection
- Explains how evolution occurs
- Individuals within a population must have characteristics that are heritable, meaning they can be passed on to offspring
- In a particular environment, certain versions of these heritable traits help individuals survive better or reproduce more than do other versions
Natural selection vs. evolutionary change
If certain heritable traits lead to increased success in producing offspring, then those traits become more common in the population over time. In this way, the populations characteristics change as a result of natural selection acting on individuals. This is a key insight: natural selection acts on individuals, but evolutionary change affects only population.
Fitness
The ability of an individual to produce offspring. Individuals with high fitness produce many offspring.
Adaptation
A trait that increases the fitness of an individual in a particular environment
The two central, unifying ideas of biology
- The cell is the fundamental structural unit in all organisms
- All species are related by common ancestry and have changed over time in response to natural selection
Speciation
When natural selection causes populations of one species today diverge and form new species
Taxonomy
- To name and classify organisms
* Flourished around 1735 with contributor, Carolus Linnaeus, a botanist
Taxonomic levels (most to least specific)
Species, genus, family, order, class, phylum, and kingdom
Binomial nomenclature
- Two part naming system
- Genus (made up of a closely related group of species) then species (individuals that regularly breed together or have characteristics that are distinct from those of other species)
Five kingdom scheme
- Monera (including all prokaryotes)
- Protista (including several groups of unicellular eukaryotes)
- Plantae
- Fungi
- Animalia
Prokaryotes vs. Eukaryotes
- Eukaryotes- Organisms with a nucleus, many are multicellular
- Prokaryotes- Organisms without a nucleus, majority are unicellular
Phylogeny
The development or evolution of a particular group of organisms
rRNA
- Made up of four smaller chemical components called ribonucleotides, A, U, C, and G, connected to one another linearly
- The ribonucleotide sequence in rRNA is a trait, that can change during the course of evolution
- Although rRNA performs the same function in all organisms, the sequence is not identical in all species
Phylogenetic tree
Shows relationships among species
Three domains of life
Bacteria, Eukarya, and Archaea
Null hypothesis
Specifies what we should observe if the hypothesis being tested doesn’t hold
Important points when designing an effective experiment
- Only one condition is changed, the one that is relevant to the hypothesis being tested
- It is critical to include control groups
- The experimental conditions must be carefully controlled
- Repeating the test is essential
Hypotheses
Proposed explanations that make testable predictions
Predictions
Observable outcomes of particular conditions
