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WGU Life Science I


a group of similar organisms that can mate with each other and produce fertile offspring

Why are there so many species?

genetic isolation

Which best describes the biological species definition/concept?

reproductively isolated

cohesion species concept

defines a species as a group of organisms that can exchange genetically; concentrates on mechanisms that maintain species as discrete phenotypic entities

What is a species?

Difficult to define. Ideally should allow one to distinguish organisms that are on independent evolutionary "paths"

What is the ecologica species concept based on?

where an animal lives and what it does

Whati sthe problem with using the morphological species concept to compare orgainisms in the fossil record?

morphological differences do not necessarily indicate genetic differences

How does genetic isolation occur?

usually physical isolation precedes genetic isolation

allopatric speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier (allo means different, patric means homeland). EX: maruspials in austrailia have no placenta mammals, marsupials everywhere else does

What are some examples of geographical distrubances that may cause allopatirc speciation?

forest fire, earthquake, formation of a canyon, continental drift

What are three mechanisms by which allopatric speciation occurs?

founder effect, genetic drift will continue, selection pressures of the new enironment

What is important about the physical barrier of allopatric speciation?

it prevents intermating between individuals in the two populations

sympatric speciation

The formation of a new species as a result of a genetic change that produces a reproductive barrier between the changed population (mutants) and the parent population. No geographic barrier is present. This happens in plants by polyploidy and some amphibians.


condition in which an organism has more than 2n sets of chromosomes

What are two major types of polyploidy?

autopolyploidy and allopolyploidy


An organism having more than two sets of chromosomes, all of which were derived from the same species (self-fertilization).


having more than 2n sets of chromosomes which are derived from two different species

___ is cause by a mistakes in either mitosis or meiosis which results from a nondisjunction of chromosomes.


Linnaeus Classification Scheme (KPCOFGS)


What makes something a species?

populations that interbreed and produce fertile offspring; breeding takes place in a wild, free-range condition


relationship between lifeforms and the geographic location where they are found

How does speciation begin?

a small population must be isolated to interrupt gene flow (geographical isolation), genetic divergence, reproductive isolation

genetic divergence

Process of one species diverging over time into more than one species

adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

What is an example of adaptive radiation?

13 species of finches on the same island

Geographically isolated populations become separate species when they are no longer able to ___ or when the resulting offspring are not viable and/or fertile.


What are some conditions that allow adaptive radiation to occur?

a population invades an island that contains a number of unexploited niches and variation in environmental conditions; when an opportunity of unexploited niches and varying habitat enable a single species to diversify into several new species.

prezygotic barriers

Reproductive barriers that prevent mating or fertilization

What are two categories of reproductive isolation?

prezygotic and postzygotic

Name 5 prezygote mechanisms.

isolation by habitat, behavioral isolation (courtship ritual), temporal isolation (time factors/seasonal), mechanical isolation (reproductive organs that don't fit), gametic isolation (recognition between sperm and egg)

Name 3 postzygotic isolation mechanisms.

hybrid viability, hybrid fertility, hybrid breakdown


a selective breeding method in which 2 genetically different individuals are crossed

What must happen for a new species to form?

two different populations that can't reproduce with each other (isolating mechanisms between populations

Two populations are classified as separate ___ when they can't produce fertile offspring in wild, free-ranging conditions.


Give some examples of some species that have evolved.

finches, mustard plant, marsupials -> opossum, lizard -> snake, dinosaurs -> birds, reptiles -> amphibians, oats, cotton, potatoes, tobacco, wheat

What are two theories which present different views as to how species arise?

gradualism, punctuated equilibrium


a model of evolution in which gradual change over a long period of time leads to biological diversity

punctuated equilibrium

pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change

What is an average lifespan of a species?

4 - 5 million years

Why is it difficult to trace speciation through time?

transition fossils are hard to find


evolution on the smallest scale—a generation-to-generation change in the frequencies of alleles within a population (natural selection, mutation, gene flow, genetic drift)


large-scale evolutionary changes that take place over long periods of time (a bunch of microevolutions, speciation starts macroevolution change)


A pattern of evolutionary change that produces biological diversity by budding one or more new species from a parent species that continues to exist; also called branching evolution.

biological species concept

definition of a species as a population or group of populations whose members can breed with one another in nature and produce fertile offspring

What are some limitations to the biological species concept?

asexual organisms, fossils (no way to evaluate the reproductive isolation of these)

What are some reasons for the extinction of a species?

habitat destruction, interbreeding, hybridization, env. pollution, catastrophes, competition, predators, disease, hunting/collecting, natural selection

What is the role of natural selection on extinction?

a species could find that it does not have traits within its gene pool to survive changes in the environment, and a sudden shift in the environment, such as a loss of habitat, a species may not been able to live long enough to reproduce; the extinct organisms were not able to adapt to the environment, and only the fittest survived

Inductive reasoning

reasoning from detailed facts to general principles

Deductive reasoning

reasoning from the general to the specific


tentative answer to a well-framed question; educated guess; must be testable and falsifiable

Scientific writing

use passive voice, verbs are present tense, scientific names are italicized, data is plural from datum, spectra is plural from spectrum, species is singular and plural, #'s greater than ten are associated with measurements should be written as numerals, number associated with a measurement should not start with a sentence, metric measurements should be abbreviated without periods


base unit of meter (length)


base unit of kilogram (mass)


base unit of second (time)


base unit of ampere (electric current)


base unit of Kelvin (thermodynamic temperature)


base unit of mole (amount of substance)


base unit of candela (luminous intensity)

How many natural elements are there in the periodic table?


What elements make up 96% of living matter?

carbon, oxygen, hydrogen, and nitrogen


anything that takes up space and mass


can't be broken dow any further by chemical reactions


substance of two or more different elements combined in a fixed ratio


smallest unit of matter that still retain the properties of an element

atomic number

number of protons

mass number

number of protons and neutrons

atomic mass

total mass of atom


an element that has the same number of protons but the neutrons increase; they behave identically in chemical reactions

radioactive isotopes

one which the nucleus decays and spontaneously gives off particles and energy


negative charge; react in chemical reactions; attracted to positive nucleus; goal is to fill electron shells; when loose energy they are pulled toward nucleus; when gain energy they move to outer shells

valance electron

electrons in outer shell of atom

valence shell

outermost shell of atom; behavior of atom depends mostly on the number of electrons in the outermost shell of atom

inert gas

elements found in group 18, do not usually form compounds because atoms do not usually gain, lose, or share electrons. (unreactive)

covalent bond

sharing of a pair of valence electrons by two atoms (H2); share electrons

Nonpolar covalent bonds

electronegativity of electrons is equally shared (H2, O2)

polar covalent bonds

one atom is bonded to a more electronegative atom, the electrons of the bond are not shared

ionic bond

where a more electronegative atom strips electrons away from its partner; transfer electrons

Compounds formed by ionic bonds are called ionic compounds or ______, which are often formed in nature as crystals.


What are two weak bonds?

ionic bond, hydrogen bond, and van der waals interactions

What is the strongest bond?

covalent bond

chemical equilibrium

reversible chemical reaction, the points where the reactants decompose and break down to meet the same amount that is formed

What atom is the basis of most biological molecules?

Carbon (enters the biosphere through plants, which use the sun to make CO2 in the atmosphere)


organic molecules consisting only of carbon and hydrogen; they are part of petroleum because of fossil fuels of living organisms long ago; they release a lot of energy; they do not dissolve in water


compounds that have the same numbers of atoms of the same element but have different structures and hence different properties

What are the six functional groups most important in the chemistry of life?

hydroxyl, carbonyl, amino, sulfhydryl, carboxyl, phosphate














adenosine triphosphate; source of energy for cell processes

What are the four main classes of large biological molecules?

carbohydrates, lipids, proteins, nucleic acids

Which of the four main classes of large biological molecules are polymers? Which are not?

Polymers: carbohydrates, nucleic acids, proteins. Not polymers: lipids

How are polymers disassembled to monomers?

hydrolysis (to break with water)

What are carbohydrates?

sugars and starches

What is an example of a monosaccharides?

simple sugars; glucose

What is an example of a disaccharides?

double sugars; maltose, lactose, fructose

What is an example of a polysaccharides?

many sugars; macromolecules (starch, glycogen, dextran, cellulose, chitin)

What is a storage or structure polysaccharide?



where plants store starch as granules within cellular structures


where animals store polysaccharides


structural polysaccharide that is a major component of tough walls that enclose plant cells


structural polysaccharide that is used by arthropods to build their exoskeleton


biological molecule is insoluble to water, consists of mostly hydrocarbons, and has no polymers

What does lipids include?

waxes, fats, phospholipids, and steroids


large molecules that are not polymers and are assembled from smaller molecules by the dehydration process; combined of glycerol and 3 fatty acids


alcohol with 3 carbons, each bearing a hydroxyl group

fatty acids

16 to 18 carbons in length; at one end is a carboxyl group then a long HC chain

Why are fatty acids hydrophobic?

the nonpolar bonds of carbon and hydrogen (ex: oil and water)


similar to fat but has only 2 fatty acids attached to glycerol rather than 3; the 3rd hydroxyl group of glycerol is joined to a phosphate group, which has a negative electrical charge


lipids characterized by a carbon skeleton consisting of four fused rings (cholesterol)


account for more than 50% of dry mass of most cells; consists of one or more polypeptides folded and coiled into specific formations; functions are storage, transport, protect, contractile, structural (shape determines function)


polymers of amino acids; proteins are all polymers constructed from the same set of 20 amino acids


type of protein that regulates metabolism by acting as catalysts; work horses of cell by running and carrying out the processed of life

amino acids

organic molecules possessing both carboxyl (-COOH) and amino (-NH2) groups

nucleic acids

DNA and RNA; Polymers assembled from individual nucleotides; used to store and transmit hereditary, or genetic, information; the two kinds of nucleic acids are ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)

DNA -> RNA -> ____



actual sites of protein synthesis

In a ____ cell, ribosomes are located in the cytoplasm, but DNA resides in the nucleus.


What conveys the genetic instructions from building proteins from the nucleus to the cytoplasm?

messenger RNA (mRNA)

___ cells lack nuclei, but they still use the RNA to send a message from the DNA to the ribosome.


What does a nucleotide consist of ?

nitrogenous base, pentose (5 carbon sugar), phosphate group


nucleic acids that exists as polymers

What are the four nitrogenous bases of nucleic acids of DNA?

A (adenosine), T (thymine) G (guanine), C (cytosine); A - T, G - C

What are the four nitrogenous bases of nucleic acids of RNA?

A (adenosine), U (uracil) G (guanine), C (cytosine); A - U, G - C

Primary structure

linear arrangement of proteins

Secondary structure

results when a polypeptide coils or folds in a particular way

Tertiary structure

results when proteins are folded giving rise to the final 3D shape

Quaternary structure

results when two or more polypeptides combine

simple hydrocarbon

consists of 4 hydrogen bonded to a carbon (CH4, methane); can have four bonds per carbon atom; building blocks from many complex molecules making up organisms

An atom with a high electronegativity is more likely to become a ____ ion.

negative (gain electrons)

The ____ of an atom is its ability to attract electrons.


Electronegativity values ___ moving up and to the right of the periodic table. Thus O is the most electronegative over N. H is the least electronegative.


Atoms with low electronegatvities are most likely to form what kind of ion?



process where ionic bonds form from the attraction of the oppositely charged ions

What type of bond does water have?

polar covalent, hydrogen bond

hydrogen bond

relatively weak attraction between a partially positive H of one molecule and the partially negative atoms of another molecule; two most common are H-O and H-N. DNA molecules have these bonds

van der wals

very weak bond; happens between tow molecules that have no polar molarity (ex: tar and oil); non-polar (carry no charge) and very tightly packed

R. Franklin and M. Wilkins

used x-ray diffraction to study DNA structure (1950)

Linus Pauling

Received the 1954 Nobel Prize from his work on genetics and atomic structure of proteins and hemoglobin; he proposed a 3 stranded DNA molecule

Watson and Crick

(1) A=T, G=C, (2) Measurements: 0.34, 3.4, 2.0, 10 bases per turn of the helix (3) bond of pyrimidines (C,T, single ring) and purine (A, G, two ring) are H-bonds


adenine and guanine; two ring structure


cytosine and thymine; single ring structure

What type of bonds do guanine (G) and cytosine (C) have?

3 bonds, hydrogen bonds

What type of bonds to adenine (A) and thymine (T) have?

2 bonds, hydrogen bonds

antiparallel structure

5 end means the 5 carbon end is facing up; 3 end means the 3 carbon end is facing up; phosphates are covalently linked to the 5 carbon


RNA; contains carbon; pentose (5 carbon) connected to the nitrogen base


DNA; does NOT contain oxygen and is a pentose (5 carbon) connected to the nitrogen base