Human, Animal, and Plant Reproduction Fertilization Fertilization is the fusion of a haploid sperm and a haploid egg Produces a diploid zygote External.
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Fertilization Fertilization is the fusion of a haploid sperm and
a haploid egg Produces a diploid zygote External fertilization occurs outside the
female’s body This is seen in fish and amphibians Because of the lack of protection and the harsh
environment, many eggs are released to ensure the species’ survival
Internal fertilization occurs inside the female’s reproductive tract
This is seen in birds, reptiles, and mammals
Embryonic Development After fertilization, the zygote begins to go through
mitosis rapidly The rapid mitotic divisions are called cleavage The zygote does not grow much in size, but
grows in cell number At first, cleavage creates a mass of cells called a
morula The morula becomes a ring of hundreds of cells
called a blastula
The center of the blastula is filled with a fluid, and is called the blastocoel
The blastula then goes through gastrulation, in which it becomes indented
The indented blastula is now called a gastrula, and has two layers
The outer layer is the ectoderm, and the inner layer is the endoderm
A third layer called the mesoderm forms between the ectoderm and the endoderm
The gastrula is now an embryo
Fertilization
egg
sperm
Cleavage starts
morulablastula
Gastrulation
gastrula
Embryo
ectoderm
mesoderm
endoderm
Differentiation In differentiation, the cells of the embryo
become specific body cells This is done by expressing certain genes and not
expressing others The ectoderm becomes the nervous system and
skin The mesoderm becomes the muscles, circulatory
system, skeleton, excretory system, and reproductive system
The endoderm becomes the lining of the digestive system and respiratory system, parts of the liver, and parts of the pancreas
Site of Development If fertilization was external, development will be
external Ex: fish embryos develop in the water Survival rate is very low, so many eggs are
fertilized The embryos’ food source is the yolk of the egg Birds and reptiles have internal fertilization, but
external development Their embryos feed on yolk as well
Their eggs have developed a shell for protection and membranes that provide a favorable environment for development
Embryonic membranes: 1. Amnion: contains the amniotic fluid that
provides a watery environment, protects the embryo from shock, and prevents the embryo from sticking to the shell
2. Yolk sac: surrounds the yolk and contains blood vessels that transport food to the embryo
3. Allantois: a respiratory membrane and a storage site for nitrogenous wastes like urea
Internal development occurs when the embryo grows inside of the body of the female
The parent provides nutrition and protection There is a relatively high survival rate, so fewer
eggs are fertilized
Placental Mammals Have internal fertilization and internal
development The embryo develops inside the uterus The eggs have very little yolk and are small
compared to the eggs of other animals The placenta forms inside the uterus from both
embryonic tissues and maternal tissues The placenta allows for the exchange of
nutrients, wastes, and respiratory gases between the mother and the embryo
The mother’s blood and the embryo’s blood never mix
Instead, materials are transported by diffusion and active transport
The umbilical cord, which contains blood vessels, connects the embryo to the placenta
Humans are placental mammals
Marsupials Marsupials are non-placental mammals Have internal fertilization and internal embryonic
development Nutrition for embryonic development does not
come directly from the mother The embryo lives off the yolk The embryo is born prematurely and completes
its development in the mother’s pouch The pouch contains the milk-producing
mammary glands
Human Gamete Production Human gametes are made in the gonads Testes in males Ovaries in females Male gametes are sperm Female gametes are eggs or ova Both gametes are made in meiosis Spermatogenesis is the production of sperm Oogenesis is the production of ova
In spermatogenesis, four sperm are made each time meiosis is done
In oogenesis, one ovum and three small polar bodies are made each time meiosis is done
The ovum is large enough to support embryonic growth
The polar bodies disintegrate
Male Reproductive System The testes are located in the scrotum outside
the body Sperm production occurs best at 1-2 degrees
below normal body temperature From the testes, the sperm move through tubes
called the vas deferens to the urethra The urethra is contained within the penis The penis allows for internal fertlization
The prostate gland, bulbourethral gland, and seminal vesicles produce liquid for the sperm as they travel through the vas deferens
The liquid makes semen, which nourishes the sperm and provides a watery environment for them to move through
The testes also produce the hormone testosterone
Testosterone regulates the maturation of sperm and the development of secondary sexual characteristics
Seminal vesicle
Vas deferens
Prostate gland
Bulbourethral gland
Penis
Urethra
Vas deferens
Epididymis
Testis
Scrotum
Female Reproductive System The ovaries produce ova in tiny cavities called
follicles The ovum is released from the ovary in ovulation
and enters one of the two Fallopian tubes (oviducts)
The uterus is where an embryo will develop The cervix is the opening of the uterus into the
vagina or birth canal
The ovaries produce the hormones estrogen and progesterone
These hormones regulate the menstrual cycle and the development of secondary sexual characteristics
Menstrual Cycle At birth, all the ova a female will ever produce
are already present in an immature form The menstrual cycle will begin at puberty and
stop at menopause The menstrual cycle is the rise and fall of
hormones that regulate the release of one ovum every 28 days
Also regulates the preparation of the uterus for pregnancy by thickening the lining of the uterus, called the endometrium
1. Follicle stage: the ovum matures in the ovary, and estrogen is releasedEstrogen causes the endometrium to thicken and
become more vascularized 2. Ovulation: the ovum is released from the
follicle and enters the Fallopian tubeMidpoint of the cycle = day 14
3. Corpus luteum stage: the empty follicle in the ovary becomes the corpus luteumThe corpus luteum releases progesterone, which
increases the thickening of the endometrium 4. Menstruation: the shedding of the
endometrium that occurs if fertilization does not take place
During the menstrual cycle, the hypothalamus in the brain and the pituitary gland also produce hormones
Follicle-stimulating hormone (FSH) causes follicle growth in the ovary and estrogen production
Estrogen production will eventually inhibit FSH Luteinizing hormone (LH) causes the growth of
the corpus luteum and the production of progesterone
Progesterone production will eventually inhibit estrogen, LH, and FSH
This regulation of hormones between the pituitary, hypothalamus, and ovaries is an example of negative feedback
Fertilization and Development Fertilization occurs in the upper one third of the
Fallopian tube If the ovum is not fertilized about 24 hours after
ovulation, it deteriorates If fertilization does occur, the zygote goes
through cleavage and travels to the uterusTakes about 6-10 days to reach the uterus
The zygote is an embryo by the time it reaches the uterus and has depleted its yolk supply
In the uterus, the embryo implants in the thick endometrium and can get nutrients from the mother
If more than one ovum was released and fertilized, fraternal twins developNo more alike than other siblings
If one zygote separates into two during cleavage, identical twins developHave the same DNA
In in vitro fertilization, the sperm and ovum are fused in the lab and then inserted into the mother’s uterusUsed when there is trouble conceiving naturally
Prenatal Development Cleavage occurs in the Fallopian tube Gastrulation occurs after the embryo has
implanted Differentiation and growth occur The placenta is the connection between mother
and embryo The amnion surrounds the embryo and contains
the amniotic fluid The umbilical cord holds the blood vessels that
carry materials between mother and embryo
Prenatal development requires the supplying of a proper balance of nutrients to the embryo
Harmful substances like alcohol, tobacco smoke, drugs, and infections can travel through the placenta and harm the fetusCan lead to life-long health problems for the fetus
Birth Birth occurs after a nine-month gestation period Strong contractions of the uterus (labor) force the
baby through the cervix and vagina The placenta is forced out of the body after the
baby is delivered The mammary glands will provide milk for
nourishment and antibodies for immunity
Asexual Plant Reproduction In vegetative propagation, a new plant grows out
of a part from an old plantSimilar to budding
People often cut stems from plants with desired traits and grow identical plants from those cuttings
Ex: a twig from an apple tree can be used to produce clones of the original tree
Parts of the Flower Meiosis and fertilization take place in the flower
of the plant The flower is specialized for sexual reproduction The male part of the flower is the stamen The female part of the flower is the pistil Flowers with both stamens and pistils are
complete flowers Flowers than have either stamens or pistils are
incomplete flowers
The stamen is made of the anther and the filament
The anther produces the haploid pollen grains The pistil is made of the stigma, style, and ovary The ovule that develops in the ovary contains the
haploid egg
Pollination Pollination is the transfer of pollen grains from
the anther to the stigma This can be done using the wind, insects, and
birds Colored petals and nectar attract pollinating
insects Self-pollination is the transfer of pollen from the
anther to the pistil of the same flower or same plant
Cross-pollination is the transfer of pollen from the anther of one plant to the pistil of another plant Increases genetic diversity
Pollen grains have thick walls to prevent dehydration as they travel
After pollination, the pollen grain germinates on the stigma and forms a pollen tube
The pollen tube travels down the stigma and into the ovule
Sperm nuclei are made and fuse with the egg
Embryo Development After fertilization, the ovule that contains the
embryo develops into a seed The seed is made of a seed coat and the embryo The ovary develops into a fruit The plant embryo has three parts: 1. Hypocotyl: becomes the root and the
lower stem 2. Epicotyl: becomes the leaves and the
upper stem
3. Cotyledons: contain stored food that will provide nutrition for the germinating plant
If a plant has one cotyledon, it is a monocot If a plant has two cotyledons, it is a dicot
Germination and Growth Seeds develop in fruit, which aid in seed
dispersal After dispersal, the seeds will germinate if the
conditions are rightSufficient moisture, proper temperature, and sufficient
oxygen After developing into a plant, growth continues at
the meristems Apical meristems are found at the tips of roots
and stems and cause an increase in length
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