Chapter 8- Reproduction Flashcards
Cell division
The process by which a cell doubles its organelles and cytoplasm, replicates its DNA, and then divides in two
Cell division in unicellular vs multicellular organisms
Unicellular: means of reproduction
Multicellular: a method of growth, development, and replacement of worn-out cells.
Mitosis
Division and distribution of cell’s DNA to its two daughter cells such that each cell receives a complete copy of the original genome
Karyokinesis is _______ and is followed by _______, which is __________
Nuclear division, cytokinesis, cytoplasmic division.
Interphase
Where 90% of a cells’s life is spent.
Period where each chromosome is replicated.
Sister chromatids formed as a result of replication and held together at a central region called the centromere.
True or false: During interphase, the individual chromosomes are not visible.
True– the DNA is uncoiled and called a chromatin
How many parts in interphase of euk. cells and what are they?
4
G1, S, G2, M
What happens during G1 phase?
It initiates interphase. Active growth phase.
Cell increases in size and synthesizes proteins.
The length of the G1 phase determines:
the length of the entire cell cycle
What happens during the S phase?
S phase is the period of DNA synthesis
What happens during the G2 phase?
The cell prepares to divide. It grows and synthesizes proteins.
What happens during the M phase?
Mitosis-Cell division occurs
Results in two identical daughter cells
What are the 6 phases of mitosis?
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
Prophase
Chromosomes condense, centrioles move towards opposite poles of the cell. Spindle apparatus forms between them, allowing spindle fibers to interact with chromosomes
What phase does the nuclear membrane first disappear?
Prophase
Metaphase
Centrioles in opposite sides.Spindle apparatus fibers attach to each chromatid at centomere– sister chromatid line up in middle
Anaphase
Shortening of spindle fibers. Centromeres and sister chromatids separate towards opposite sides of the cell.
Telophase
Spindle apparatus disappears. Nuclear membrane forms around each set of chromosomes. Chromosomes uncoil
Cytokinesis
Cytroplasm divides– cleavage furrow formed.
2 major different between cell division in animal cells and plant cells
- Plant cells lack centrioles– spindle apparatus synthesized by microtubule organizing centers that are not visible.
- Different type of cytokinesis- no cleavage furrow– they form a cell plate.
What is a cell plate?
In plants– an expanding partition that grows outward from the interior of the cell until it reaches the cell membrane.
Basic difference between meiosis and mitosis:
Two parents involved in meiosis instead of just one in mitosis. Mitosis preserves the diploid # of the cell whereas meiosis produces haploid #– halving the # of chromosomes.
Meiosis
Process by which sex cells are produced. Divisions of two primary sex cells resulting in four haploid cells called gametes.
Interphase– Meiosis
Parent cell’s chromosomes are replicated– reslting in the 2N number of sister chromatids
Prophase 1- meiosis
- Chromatin condenses to chromatins, spindle apparatus forms, and the nucleoli and nuclear membrane disappear.
- Synapsis/ crossing over takes place.
Tetrad
Synaptic pair of homologous chromosomes– contains 4 chromosomes.
True or false: sister chromatids are identical after crossing over takes place
False
Metaphase 1
Homologous pairs (tetrads) line at the equatorial plane and each pair attaches to a separate spindle fiber by its kinetochore.
Anaphase 1
Homologous pairs separate and are pulled to opposite poles of the cell (disjunction).
Either maternal or paternal chromosome can end up in daughter cell.
Telophase 1
A nuclear membrane forms around each new nucleus. At this point, each chromosome still consists of sister chromatids joined at the centromere.
Is meiosis 2 preceded by chromosomal replication?
No.
What happens during the second meiotic division?
The chromosomes align at the equator, separate, and move to opposite poles and are surrounded by a reformed nuclear membrane.
Asexual reproduction is..
the production o offspring without fertilization. New organisms are formed by division of a single parent cell
What organisms reproduce asexually?
Prokaryotes. Among animals, more prevalent in invertebrates than vertebrates. All plants
What are the 4 types of asexual reproduction?
- Fission
- Budding
- Regeneration
- Parthenogenesis
Fission
Seen in proks
DNA replicates and a new plasma membrane and cell wall grow inward along midline of the cell.
Budding
Replication of nucleus followed by unequal cytokinesis. The cell membrane pinches inward to form a new cell that is smaller in size but genetically identical to parent. This “bud” eventually grows into an adult.
Fission occurs in…?
Single-celled organisms such as amoeba, paramecia, algae, and bacteria.
Budding occurs in?
Hydra and Yeast
Regeneration
Regrowth of a lost or injured body part by mitosis
Regeneration occurs in
Hydra, starfish, salamanders, tadpoles
Parthenogenesis
Development of an unfertilized egg into an adult organism.
Parthenogenesis occurs in:
Most species of bees and ants (MALES)
Working bees and females are produced sexually.
Alternation of generation
In plants– a diploid number is followed by a haploid generation.
Circle of alternation of generation–
A diploid sporophyte produces haploid spores, which develop into haploid gametophytes, which produce a haploid gamete. The two haploid gametes sexually produce the sporophyte generation.
Spores
Specialized cells with hard coverings that prevent the loss of water
Meristems
Undifferentiated tissues in plants. Provide a source of cells that can develop into an adult plant
Natural Vegetative propagation types
Bulbs
Tubers
Runners
Rhizomes
Bulbs
Split to form several bulbs. This occurs in tulips and daffodils
Tubers
Underground stems with buds- like eyes of potatoes, that can develop into adult plants
Runners
Stems running above ground- can produce new roots and upright stems- strawberry and lawn grass
Rizomes
Also called stolons. Woody underground stems. They can develop new upright stems as they do in ferns and iris plants.
Types of artificial vegetative propagation
Cut
Layering
Stem of one plant attached to another
A cut piece of stem can develop…
new rots in water or moist ground
Auxins
Synthetic plant hormones that can be used to accelerate root formation
Layering
Bend stems of certain plants to the ground and cover in soil– will take root
3 artificial vegetation
The stem of one plant (scion) can be attached to the rooted stem of another closely related plant (stock)– The cambium of both stems must be in contact
Gonads
Organs where gametes are produced.
Male gonads are..
testes- produce sperm in the rightly coiled seminiferous tubules
Female gonads are..
Ovaries– produce oocytes
Hermaphrodites
Have both functional male and female gonads– include the hydra and earthworm
Spermatogenesis occurs in the..
Sperm production- occurs in the seminiferous tubules. Di
Spermatagonia
Diploid cells go through meiosis to produce 4 haploid cells
Parts of a sperm..?
Head- consists of nucleus
Tail- flagella- propels sperm
Mitochondria- in neck and body- provide energy
Oogenesis
Production of female gametes
Each meiotic division in oocyte produces
A single mature egg and a polar body- which degenerates
Fertilization
Union of the egg and sperm nuclei to form a zygote with a diploid number of chromosomes
External fertilization occurs in
vertrebrates that reproduce in water
What is external fertilization
Female lays eggs and male deposits sperm in close vicinity– swim through water to eggs
What is internal fertilization?
Practiced by terrestrial vertrebrates and provides a direct route for sperm to each the egg
Testes are located in a pouch called the
scrotum
Sperm travels through the
SEVENUP
The testes are a side of production of
testosterone
Testosterone
Regulates secondary male characteristics including facial, pubic hair and voice changes
Steps of spermatogenesis
Spermatogonia–> mitosis which produce primary spermatocytes—> meiosis 1 which prouduce secondary spermatocytes—> meiosis 2 which produce 4 haploid spermatids
acrosome
A caplike structure derived from the golgi apparatus– contains enzymes to penetrate egg.
Where are the ovaries found?
In the abdominal cavity, below the digestive system
Follicle
Multilayered sac of cells that contained, nourishes and protects all immature ovum. Produce estrogen.
What happens once a month in women?
An immature ovum is released and drawn into the oviduct (tube)
The site of fetal developement
uterus
Cervix
connects with vaginal canal, site of sperm deposition
steps of oogenesis
- At birth, all of the immature ova, known as primary oocytes that a female will produce in her lifetime are already in her ovaries
- Are diploid cells
- After menarche, one primary oocyte per month completes meiosis I, yielding two daughter cells of enequal size
- secondary oocyte is expelled from follicle during ovulation– MII does not occur until fertilization
Two layers of cells that surround the oocyte cell membrane
- Zona Pellucida- inner
2. Corona radiata- outer
Meiosis II is triggered in oocytes when
The inner and outer layer (ZP and CR) are penetrated by the sperm.
What does meiosis 2 of oocyte result in?
A mature ovum and a polar body
The secretion of both estrogen and progesterone regulated is regulated by
LH and FSH, which inturn are regulated by GnRH
Estrogens
Steroid hormones necessary for normal female maturation
stimulate development of female reproductive tract and contribute to the development of secondary sex characteristics and sex drive
What is responsible for the thickening of the endometrium (uterine) wall?
Estrogens
Progesterone
Steroid hormone secreted by corpus luteum during the luteal phase of menstrual cycle.
Stimulates the development and maintenance of the endometrial walls in prep for implantation
What are the 4 phases of the menstrual cycle?
- follicular phase
- ovulation
- luteal phase
- menstruation
Follicular phase
Begins with the cessation of menstrual flow
FSH promotes developement of follicle which grows and begins secreting estrogen
Ovulation
Midway through the cycle
Mature ovarian follicle bursts and releases an ovum
caused by surge in LH– following high estogen levels
Luteal phase
after ovulation
LH surge causes ruptures follicle to develop into corpus luteum- which secretes estrogen and progesterone
Progesterone- causes glands of endometrium to mature and produce secretions that prepare it for implantation of an embryo
Progesterone and estrogen are necessary to maintain
the endometrium
Menstruation
If ovum is not fertilized, corpus luteum atrophies– endometrium sloughs off
What happens if fertilization does occur?
Developing placenta produces hCG, maintaining the corpus luteum an supplies estrogen and progesterone to maintain uterus until placenta takes .
The acrosome is responsible for penetrating
THE INNER LAYER– zona pellucida
Acrosomal process
Once in contact with the inner layer, the sperm form a tubelike structure called this, which extends to the cell membrane and penetrates it, fusing the sperm cell membrane with that of the ovum.
When does the ovum complete meiosis II?
When the sperm nucleus enters the ovum’s cytoplasm
Cortical reaction in the ovum
Caused by the acrosomal reaction– calcium ions released into the cytoplasm– results in the formation of the fertilization membrane.
Fertilization membrane
Hard layer that surrounds the ovum cell membrane and prevents multiple fertilizations
Another function of the release of Ca 2+
stimulates metabolic changes within the ovum, and greatly increases metabolic rate
Fusion of the sperm nucleus with the ovum nucleus forms a
Diploid zygote– first mitotic division of the zygote soon follows
Monozygotic twins form from
a single zygote splitting into two embryos
If single zygote slpits at the two-cell stage then:
embryos will have separate chorions and placentas
If single zygote splits at the blastula stage then:
embryos will have only one chorionic sac and will therefor share a placenta
Dizygotic twins
- Dizygotic twins result when two ova are released in one ovarian cycle and are fertilized by two different sperm.
- Two embryos implant in the iterine wall indv
Gametophyte generation
haploid gametophyte generation produces gametes by mitosis- union of male and female gametes at fertilization restores the diploid sporophyte generation.
The gametophyte reproduce
sexually
sporophytes reproduce..
asexually
Mosses- Dominant generation
Gametophyte is the dominant generation
The sporopyte in moss is
a smaller, short lived generation that depends on the gametophyte for energy and nutrients
ferns
sporophyte generation is dominant and familiar form.
Sporophyte releases sports that develop into gametophytes
Angiosperms
Flowing plants- have gametophytes consisting of a few cells that exist for very short time
woody plants (maple, rose, etc) is the _____ stage
sporophyte
Flower
reproductive structure of angiosperm
Stamens
Male organ of the flower-consists of a thin, stalk-like filament with terminal sac called the anther
Anther
Produces monoploid spores that develop into pollen grains
Three parts of a stamen
Pollen grains
anther
filament
4 parts of a pistil
stigma
style
ovary
ovules
Embryos are formed when
the zygote divides mitotically to form cells of the mass of cells (embryo)
What are the 5 parts of a plant embryo
epicotyl cotyledons hypocotyl endosperm seed coat
epicotyl
precursor of the upper stem and leaves
hypocotyl
develops into the lower stem and root
endosperm
grows and feeds the embryo. In dicots, the cotyledon absorbs the endosperm
Seed coat
Develops from the other covering of the ovule. The embryo and seed coat comprise the seed.
cotyledons
Seed leaves
dicots-2 seed leaves
monocots- 1
Most seeds develop in the
fruit
Where is the fruit formed?
the ovary walls, the base of the flower and other consolidated flower pistil components
The fruit enables the seed….
to be carried more frequently or effectively by air, water, or animals.
The seed is released from the
ovary and will germinate under proper conditions of temperature, moisture, oxygen
Growth in higher plants is restricted to
the embryonic (undifferentiated) cells called meristem cells
Apical meristems
found in the tips of roots and stems. Growth in length occurs only at these points
lateral meristem
Also called cambium- located between xylem and phloem. Permits growth in diameter and can differentiate into new xylem and phloem cells.
Lateral meristems are predominant in
woody dicots like oaks
Lateral meristems are not active tissue in
monocots (grass) and herbaceous dicots (alfalfa)
