biology lab practical

steps of the scientific method

1.ask a question
2. do background research
3. form hypothesis
4. test with experiment
5. analyze results
6. draw conclusion
7. communicate results

what is discover based science

describes nature, Requires inductive reasoning.
Goal is to gather information and often leads to a hypothesis little to no manipulated variables

hypothesis based science

Starts with observation but then asks a testable question.
Answers "how" and "why" questions.
Has independent and dependent variables

Independent variable

factor that is changed by the experimenter

Dependent variable

changes as a result of
manipulating the independent variable , the

Controlled variables

constant throughout the


No membrane bound organelles or nucleus.
Always single celled
Bacteria and archaea


Membrane bound nucleus and organelles.
More specialized and complex than prokaryotic
Plants and animals.


Independent or aggregate


Dependent on other cells


organisms that synthesize their own food


organisms that cannot synthesize their own food and rely on other organisms for nutrition

compound microscope

c elegans

Cheap and easy to care for.
Quick generation times.
(3-5 days to become an adult for C.elegans)
Transparent bodies.
1st eukaryotic organism to have its entire genome sequenced.
Share biological characteristics with humans


Blunt tail
Gonad contains sperm


Tapered tail
Oocyte in gonad

3 reasons cell division is important


stages of the cell cycle

I: Preparation for division, includes G1, S & G2.
G0: Resting cycle. Cell has left the replication cycle.
G1: Cells increase in size. Most of cell's proteins have been synthesized.
S: DNA Replication occurs.
G2: Continued cell Growth
M: mitosis, cell divi

which cell undergoes binary fission

Prokaryotes undergo
binary fission

which cells undergo mitosis

Eukaryotes undergo

which cells undergo meiosis

Sexually reproducing
eukaryotes also undergo

mitosis purpose

to make genetically identical daughter cells

mitosis importance

growth, cell reproduction, tissue regeneration

mitosis stages

1.) Prophase
2.) Metaphase
3.) Anaphase
4.) Telophase

meiosis importance

increased genetic
diversity, continued evolution

meiosis stages

1.) Prophase I 2.) Metaphase I
3.) Anaphase I 4.) Telophase I
5.) Prophase II 6.) Metaphase II
7.) Anaphase II 8.) Telophase II

mechanisms that cause genetic variation during meiosis

Crossing over:
Exchange of genetic material between chromosomes ->unique chromosomes, new combinations of genes
Independent assortment:
Chromosomes from each parent assort randomly into daughter cell .
result of random line-up of chromosomes
combination o

crossing over

Exchange of genetic
material between homologous
Results in recombinant chromosomes
Occurs in Prophase 1

Observed matches expected

alternative hypotheses

Observed does not match expected

Mendel's laws

Law of segregation
Law of independent assortment
Law of dominance

Law of Segregation

Every organism has 2 alleles per trait
When gametes form (meiosis), alleles separate
Offspring only inherits one allele from each parent

Law of Independent Assortment

Each alleles in a pair separates independently
Allele inherited is a matter of chance
Result of independent movement of chromosomes in meiosis

Law of Dominance

Some alleles are dominant, some recessive
Organisms with at least one dominant will display the
phenotype of the dominant allele


While looking at one trait, you can determine the dominant and recessive allele.
Parents are heterozygous.
Gives a phenotypic ratio of 3:1 and genotypic of 1:2:1

dihybrid cross

Looks at two traits.
Phenotypic ratio of 9:3:3:1