Biology Unit Review Questions #1
1. How is binary fission different from mitosis?
Binary fission is used only in prokaryotic cells. Prokaryotic cells usually only
have 1-3 chromosomes and no nucleus. Therefore, binary fission is faster
than mitosis because there is less time spent dissolving the nuclear
membrane, reforming the nuclear membrane, and copying large amount of
chromosomes.
2. Sketch the phases of mitosis (at least 1 sketch from each phase) and describe what is happening
in each one.
Something like this….
Prophase
• nuclear
membrane
disappear
• Spindle fibers
come from the
centrioles and
attach to opposite
sides of the
centromeres
Metaphase
• The spindle fibers
position all of the
chromosomes at
the middle of the
cell
• Each
chromosomes is
attached to a
spindle fiber from
both ends
Anaphase
• The spindle fibers
contract, the
chromosomes are
divided in 2
• Chromatids are
pulled to
opposite sides of
the cell
Telophase
• There are
matching sets of
genetic material
at each end of
the cell
• Spindle fibers
disappear (not
needed)
• Nuclear
membranes
begin to reform
around the
chromosomes,
they unravel
• The total cell
structure starts
to divide:
cytokinesis
3. Why is mitosis important in the cell cycle?
Mitosis is an important part of the cell cycle because it allows cells
to grow and multiply. It is when cells reproduce.
4. What would happen to humans if mitosis didn’t happen?
If mitosis didn’t happen humans would not be able to grow or
heal. If we were cut or broke a bone, we would die. Also, if you
think about it, we would not progress past single celled organisms.
5. What would happen to humans if meiosis didn’t happen?
If meiosis didn’t happen, humans would not be able to produce
gametes (sperms and eggs), so we would not be able to reproduce
sexually. If we are not able to reproduce sexually, we would lack
genetic diversity, and not be able to fight off diseases, or adapt to
different environments the way that we do.
6. What are the ways that organisms can reproduce asexually? Describe them.
Binary Fission

Mitotic Division

Fragmentation

Cell “pods” or budding



Plants

Like mitosis, 1 cell divides into 2 cells, except the
prokaryotic cells have no nucleus
Eukaryotic single celled organisms divide using mitosis
(all 4 phases)
Fungi send out hyphae which are like tiny hair-like vines
which grow into the surrounding material
When it breaks off it becomes a new organism
Animals can reproduce through budding where another
organism starts to grow on the side of another
Pods are a different way, where small packages of cell
can be released in to the environment to grow into a
new individual
Can send out runners (small vines) which when it breaks
off becomes its own organism
7. What could happen if chromosomes did not separate properly during anaphase in mitosis?
If chromosomes did no separate properly during anaphase, a cell could end
up with extra DNA/chromosomes or missing chromosomes. If there is
missing information the cell may not be able to survive/ do it’s job. If there
is extra, same problem except it could also result in mutations in the cell.
8. How can you explain the difference between the processes of a nerve cell and a skin cell, the
skin cells reproduce frequently, but the nerve cells only rarely.
The cell cycle of a skin cell is likely much faster than a nerve cell.
9. Why do fish lay their eggs in water?
MOST fish fertilize externally, so the female can lay eggs in the water, and
the male can release the sperm over top. (I know, ALSO they live in water….
But think of reproductive reasons…)
10. Which would you expect to lay more eggs at one time and why? A salamander (external
fertilizer) or a lizard (internal fertilizer)
The salamander, because there is a greater chance that some eggs will not
be fertilized when fertilization is external, so there is “extra”
11. The body cell of organism X has 18 chromosomes. How many chromosomes are in the eggs cell
of that organism?
The body cells are diploid, the eggs cells are haploid. There will be 9
chromosomes in the egg cell.
12. Reem says that plant pollination where animals move the pollen is better than when wind
moves the pollen. Do you agree or disagree? Explain.
Could be either. I would say that an animal can carry the pollen much
further than a breeze could, but if we are talking about a STRONG WIND
then it will likely be better than the animal.
13. Why is genetic variety important to a population? What happens in communities such as
purebred dogs where genetic variety is lost?
Genetic variety is important because it allows species to adapt to a greater
environment and fight sicknesses. Populations with low genetic variety like
purebred dogs, have a lot of genetic diseases because their genes are so
similar. They are also less able to fight illnesses.
14. Make 2 tables. In the first show the Pros and Cons of asexual reproduction, in the second show
the Pros and Cons of sexual reproduction. Based on that you see here, what kind of
reproduction is most effective?
We have done this, it’s in your notes.
15. What the causes of mutations? (notes #9)
Mutations can happen naturally during the copying of DNA during mitosis
and meiosis or because of environmental agents (mutagenic agent) such as:
radiation, chemical exposure, or temperature extremes.
16. Draw and explain the 4 different ways mutations can occur? (notes #9: reversal, deletion,
duplication, replacement).
Check your notes for diagrams, they can be very simple. A very simple
explanation is enough, ie. the genes switch places, some of the genes are
lost, part of the chromosome is switched, some of the genes are doubles.