Name:
_______________________
Block:
_____
Date:
____________________
Asexual Reproduction
A. ASEXUAL REPRODUCTION. Asexual reproduction is a type of reproduction in which a single
parent organism produces offspring that are genetically identical to itself. Unlike in sexual reproduction,
asexual reproduction involves only one parent, not two, and there is no fusing (joining) of cells such as
egg and sperm. This means that while you are genetically different from your parents, whereas an
organism produced by asexual reproductions will be genetically the identical to its parent.
Asexual reproduction results from mitotic cell division (mitosis) in eukaryotes, and via binary
fission in prokaryotes. During mitosis, one cell, called the parent cell, divides into two identical
daughter cells. Asexual reproduction can occur in unicellular (single celled) organisms like yeast, or
multicellular organisms like plants and animals. In unicellular eukaryotes like yeast, the cell simply
undergoes mitosis. A prokaryotic cell like a bacterium will undergo a similar process called binary
fission. In multicellular organisms, many cells undergo many mitotic cell division, resulting in a new
multicellular organism. Regardless of the method, the new organisms, called offspring, are genetically
identical to the parent..
Asexual reproduction is more common in invertebrate animals (animals without backbones) than in
vertebrate animals (those with backbones). Unicellular and multicellular plants can reproduce both
asexually and sexually. Types of asexual reproduction include binary fission, mitosis, budding, spore
formation, regeneration, fragmentation, vegetative propagation, and cloning.
---------------------------------------------REVIEW QUESTIONS-------------------------------------------------1.
What is asexual reproduction?
2.
What are some differences between asexual and sexual reproduction
3.
a)
In prokaryotes, asexual reproduction occurs through the process of ____________________.
b)
In eukaryotes, asexual reproduction occurs through the process of ____________________.
c)
Give an example of a unicellular prokaryote. _____________________________________.
d)
Give an example of a unicellular eukaryote. _____________________________________.
4.
List 8 forms of asexual reproduction.
1
B. BINARY FISSION is the simplest type of asexual reproduction. In binary fission, a prokaryote
divides into two equal cells, but the parent is lost in the process (Figure 1.15). Bacteria reproduce
asexually using binary fission. This process is simpler than mitosis because bacteria have no nuclear
membrane that needs to disappear and reform during the cell division process. Additionally, bacteria
have only a single loop of DNA, rather than multiple chromosomes which also makes binary fission
simpler than mitosis.
---------------------------------------------REVIEW QUESTIONS-------------------------------------------------5.
In what kind of organisms does binary fission occur? Give an example of this type of organism.
6.
List the steps of binary fission.
7.
In what ways is binary fission simpler than mitosis?
8.
What does it mean when we say that a bacterial population increases “by a factor of 2”?
2
C. MITOSIS. Mitosis is the simplest type of asexual reproduction found in eukaryotes. During cell
division a one-celled eukaryote divides by mitosis and cytokinesis* to form two daughter cells of equal
size. Both the nucleus and the cytoplasm divide equally. The chromosomes of the offspring are identical
to that of the parent. Unicellular eukaryotes like amoebas and paramecia, reproduce by mitosis.
*The process of cell division in eukaryotes actually takes place in two steps: mitosis and then
cytokinesis. Mitosis specifically refers to the division of the nucleus (the chromosomes) whereas
cytokinesis refers to the division of the of the cytoplasm by the pinching off of the two cells from one
another. When we refer to this type of asexual reproduction however, we just call it “mitosis” and
assume our audience knows that we mean “mitosis and cytokinesis”
cytoplasm
divides
---------------------------------------------REVIEW QUESTIONS-------------------------------------------------9.
In eukaryotes, cell division involves both mitosis, the division of the ____________________ and
cytokinesis, the division of the ___________________________.
10. What category of organisms reproduce asexually by mitosis?
‘
MITOSIS AND
CYTOKINESIS IN A
PARAMECIUM
11. Give two examples of organisms that reproduce by mitosis.
3
D. BUDDING. A type of asexual reproduction in which a new organism develops as an outgrowth
of the parent is called budding. The new organism, called the bud, is a tiny duplicate of the parent
organism. In budding the nucleus divides equally and the cytoplasm divides unequally. The bud and the
parent may separate from each other or may remain together and form a colony. Budding (Figure 19-2)
occurs in unicellular organisms (yeast) and in multicellular organisms (hydra). Budding in unicellular
organism is similar to mitosis, but in budding the nucleus divides equally and the cytoplasm divides
unequally. In multicellular organisms, mitosis occurs many, many times to create many, many new cells
that together form the bud. Regardless, the offspring is always smaller than the parent.
---------------------------------------------REVIEW QUESTIONS--------------------------------------------------
12. A key feature of budding is that the offspring (the ________) is _______________________ than
the parent organism.
13. Unicellular budding, the division of the _______________________ is equal and the division of
the __________________________ is unequal.
14. A unicellular organism that reproduces by budding is ______________________________.
15. ______________________________ is a multicellular organism that reproduces by budding.
…..to be continued!
4
Name:
_______________________
Block:
_____
Date:
____________________
Asexual Reproduction…continued
E. SPORE FORMATION. Spores are specialized asexual
reproductive cells that contain a nucleus and a small amount of
cytoplasm. Spores are produced by a process similar to mitosis
and unicellular budding and they contain all the genetic
information of the parent organism. However spores have an
additional feature: they are surrounded by tough protective
coats that enable them to survive unfavorable conditions, such
as extreme heat or cold, for long periods of time. When
environmental conditions become favorable each spore can
develop into a new organism. The new organism has the same
genetic makeup as its parent. Spore formation occurs in fungi
such as bread mold and mushrooms, as well as in some plants
like mosses and ferns.
spore
clusters
---------------------------------------------REVIEW QUESTIONS-------------------------------------------------16. What is a spore? How is it different from a regular cell?
17. What is an advantage of spore formation as a reproductive strategy?
18. List four organisms that reproduce by spore formation.
5
F. FRAGMENTATION.
Fragmentation is when an organism is split into fragments, and each
fragment grows into a complete, individual organism that is a clone of the original organism. For
example, in starfish a single arm can develop into a new starfish. Many rounds of mitosis and
cytokinesis go into making the new cells that allow the animal to regrow from a fragment. Other animals
that can reproduce by fragmentation are hydra and planaria.
A cautionary tale: Starfish eat oysters. Oyster fishermen once tried to kill starfish by cutting them into
pieces. Instead of dying, each starfish piece grew into a new starfish. Doh!
Fragmentation in Starfish
Fragmentation in Hydra
Fragmentation in Planaria
---------------------------------------------REVIEW QUESTIONS-------------------------------------------------19. What is fragmentation?
20. Name three animals that reproduce by fragmentation.
6
G: REGENERATION. Regeneration is the replacement of lost body parts. For example, lobsters
are able to grow a new claw to replace one that has been lost. Small lizards, such a geckos, often have
the ability to lose and regenerate a tail. This is an adaptive ability, as it allows them to escape a predator
that has caught them by the tail. Amphibians such as salamanders and newts are masters of
regeneration, and are usually able to regenerate both tails and limbs. Many rounds of mitosis and
cytokinesis go into making the new cells that allow the animal to regenerate a body part.
\
---------------------------------------------REVIEW QUESTIONS-------------------------------------------------21. Describe the process of regeneration.
22. List 4 animals that can regenerate body parts.
7
H. VEGETATIVE PROPAGATION. Vegetative propagation (also known as vegetative
reproduction) is a form of asexual plant reproduction. In vegetative propagation a part of a plant, a root,
a stem, or a leaf, grows into a new plant. The new plant is exactly the same as the parent plant.
Commercial growers use vegetative propagation rather than seeds when they want to be sure that the
offspring is identical to the parent. Seedless fruits and vegetables have to be reproduced by this method.
Growers use this type of reproduction because it is fast, easy to use, and usually successful.
Vegetative propagation can occur naturally or artificially. Natural vegetative propagation occurs
naturally without human interference. Types of natural vegetative propagation include tubers, runners,
rhizomes, and bulbs. Artificial vegetative propagation occurs as a result of human activities. Two
common methods of artificial vegetative propagation are cuttings and grafting (see table below). All
forms of vegetative propagation involve many rounds of mitosis and cytokinesis to allow the new plants
to grow.
Runners are stems that grow out over the surface
of the soil from the existing stem. At points along
the runner, new plants grow. Runners occur in
strawberries, some grasses, and spider plants.
Bulbs are underground stems specialized for food
storage. The food is stored in the thick leaves of
the bulb. Each bulb can develop into a new plant.
Onions and tulips are bulbs.
Shoots
shoot
eye
Some plants have underground stems that contain
stored food (“tubers”). Examples are potatoes and
yams. The “eyes” of the potato or yam develop
and grow into shoots .
Rhizomes are long modified stems that grow
horizontally under the soil. Lawn grasses, ferns
and irises reproduce by rhizomes.
People make cuttings of plants. The pieces of
roots, stems or leaves develop into new plants
under proper conditions. Roses, sugar cane,
bananas and pineapples are all examples of
plants that can be propagated in this way.
A cutting from one plant, called the scion, is
attached to the main body of a rooted plant called
the stock. The scion keeps its own identity.
Apples, seedless oranges and grapes are
examples of plants that can be propagated by
grafting.
8
---------------------------------------------REVIEW QUESTIONS-------------------------------------------------23. What is vegetative propagation?
24. List 4 forms of natural vegetative propagation.
25. List 2 forms of artificial vegetative propagation.
26. Match the organism(s) to the type of vegetative propagation.
Plants
Type of vegetative propagation
Onions, tulips
RHIZOMES
Roses, sugar cane,
bananas, pineapples
GRAFTING
Potatoes, yams
CUTTINGS
Strawberries, grasses,
spider plants
RUNNERS
Apples, seedless oranges,
seedless grapes
Lawn grasses, ferns, irises
BULBS
SHOOTS
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---------------------------------------------OVERALL REVIEW--------------------------------------------------
10
---------------------------------------------OVERALL REVIEW--------------------------------------------------
n
m
o
Part B. Fill in the blanks.
1.
Reproduction involving one parent is called _______________________ reproduction.
2.
In eukaryotes, the nucleus and cytoplasm divide equally during the type of asexual reproduction
known as ________________________.
3.
A type of asexual reproduction in which a new organism develops as an outgrowth of the
parent is called ____________________________.
4.
Strawberries reproduce asexually by _____________________ ________________________.
Specifically, strawberries use ______________________ to reproduce.
5.
A _______________________ is a modified stem that grows horizontally under the soil.
6.
Seedless fruits are propagated by _____________________ ________________________.
7.
The ability to replace a lost body part is called __________________________.
8.
____________________ are pieces of roots, stems, or leaves that develop into new plants.
9.
Bread mold reproduces asexually by the process of ____________ ________________________.
10. Commercial growers use ____________________ __________________________ rather than
seeds when they want to be sure the offspring are identical to the parent.
11. An onion is an example of a ______________.
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Part B. Fill in the blanks.
12. ______________________ , ________________________ and _______________________
can reproduce by fragmentation.
13. Stems that grow out over the surface of the soil from the existing stem are called
_______________________.
14. _______________________ are specialized asexual reproductive cells that are surrounded by a
tough protective coat.
15. The eyes on potatoes will develop into ______________________.
16. The __________________ is the rooted portion of a graft.
17. The __________________ is the added on part of the graft.
18. Amoebae and paramecia reproduce asexually by _____________________.
18. Mushrooms reproduce asexually by means of ________________________ .
19. In unicellular organisms, equal division of the nucleus along with unequal division of the
cytoplasm occurs during the process of ______________________.
20. The process of growing a whole new plant from a piece of root, stem, or leaf is called
_______________________ .
…to be continued!
12
Name:
_______________________
Block:
_____
Date:
____________________
Asexual Reproduction…part III
-----------------------------------------------OVERALL REVIEW-------------------------------------------------Part C: Important Terms
Define the following terms in the spaces provided.
asexual reproduction _________________________________________________________________
__________________________________________________________________________________
binary fission _______________________________________________________________________
__________________________________________________________________________________
bulbs _____________________________________________________________________________
__________________________________________________________________________________
cuttings____________________________________________________________________________
__________________________________________________________________________________
fragmentation_______________________________________________________________________
__________________________________________________________________________________
grafting ___________________________________________________________________________
__________________________________________________________________________________
mitosis_____________________________________________________________________________
__________________________________________________________________________________
regeneration ________________________________________________________________________
__________________________________________________________________________________
rhizomes __________________________________________________________________________
__________________________________________________________________________________
runners ____________________________________________________________________________
__________________________________________________________________________________
asexual reproduction _________________________________________________________________
__________________________________________________________________________________
scion _____________________________________________________________________________
__________________________________________________________________________________
shoots _____________________________________________________________________________
__________________________________________________________________________________
spore formation _____________________________________________________________________
__________________________________________________________________________________
stock _____________________________________________________________________________
__________________________________________________________________________________
vegetative propagation________________________________________________________________
__________________________________________________________________________________
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Part D: MULTIPLE-CHOICE QUESTIONS
1.
Which method of plant reproduction is illustrated by the diagram at the right?
(A) bulbs
2.
(B) grafting
(C) cuttings
(B) grafting
(C) fragmentation
(B)
(B) gametes
(C) spores
(D) grafts
(B) budding
(D) fertilization
Which of these forms of plant reproduction is likely to produce a new plant that is different from
the parent plant?
(A) cuttings
9.
(B) is commonly called sexual reproduction
(D) is found in unicellular organisms
By which process is the organism shown
in the diagram to the right reproducing?
(A) fragmentation
(C) regeneration
8.
(D)
Special reproductive cells that can withstand unfavorable environmental conditions are called
(A) buds
7.
(C)
Vegetative propagation is a method of reproduction which
(A) occurs in some multicellular plants
(C) results in genetically unlike offspring
6.
(B) plant embryos produced by fertilization
(D) gametes produced in the ovary
Which diagram shown below represents reproduction by means of runners?
(A)
5.
(D) binary fission
Which process represents asexual reproduction of plants?
(A) geraniums produced from cuttings
(C) maple trees produced from seeds
4.
(D) runners
A missing part of a starfish or a planarian can be regrown by the process known as
(A) budding
3.
Circle the best answer
(B) seeds
(C) bulbs
(D) runners
Red tulips are seldom grown from seed for commercial distribution because
(A) the plants do not produce seeds
(C) plants grow slower from bulbs
(B) seeds may not be genetically like the parent plant
(D) seeds take too long to germinate
14