Chpter 46 Reproduction Flashcards
What is sexual reproduction?
Sexual reproduction is the creation of offspring by the fusion of a male gamete (sperm) and a female gamete (egg) to form a zygote.
What is asexual production?
The creation of offspring without the fusion of egg and sperm.
How do invertebrates reproduce?
They reproduce asexually by fission (separation of a parent into two or more individuals of about the same size.)
What is budding?
In budding, new little ones grow from parts of bigger ones.
- Budding is not considered diverse.
What is fragmentation, and what happens?
Fragmentation means breaking the body into pieces, and some or all of those pieces grow into adults. To happen, fragmentation needs regeneration, which is the regrowth of lost body parts.
What is Parthenogenesis?
Parthenogenesis is when a new individual grows from an egg without needing a father to fertilize it.
sexual reproduction
Sexual females have half as many daughters as asexual females. This is called the “twofold cost” of sexual reproduction because sexual females invest more resources in making offspring. Even though sexual reproduction is more costly, almost all types of living things with cells that have a nucleus (eukaryotic species) still reproduce this way.
What advantages does sexual reproduction have?
- genes mix up which causes many benefits.
- When offspring have more variety, it helps parents because they are more likely to have some babies that can survive in different environments that keep changing.
- An increase in the rate of adaptation
- Mixing up genes and getting rid of bad ones from a group of creatures.
Reproductive cycles are controlled by?
- Reproductive cycles are controlled by hormones and environmental cues
- Most animals exhibit reproductive cycles related to changing seasons
- Because seasonal temperature is often an important cue in reproduction, climate change can decrease reproductive success
ovulation
This is when a female’s body releases an egg that’s ready to be fertilized.
reproductive cycles
- Ovulation: This is when a female’s body releases an egg that’s ready to be fertilized.
- Midpoint of a female cycle: A female’s body goes through a monthly cycle, and ovulation usually happens in the middle of this cycle.
- Reproductive cycles related to changing seasons: Many animals have times of the year when they’re more likely to have babies. They might do this when the weather is good and food is plentiful, like in spring or summer. So, their baby-making schedule is linked to the seasons.
parthenogenesis that involves the doubling of chromosomes after meiosis
means a female can make babies on her own by making special eggs with extra genetic material.
what is hermaphrodites ?
Hermaphroditism is when one living thing has both male and female reproductive parts. This means they can make both eggs and sperm. So, when two hermaphrodites meet, they can mate and exchange both eggs and sperm to make babies. Some hermaphrodites can even fertilize their own eggs without needing another partner.
sex reversals
Sometimes, in certain species, individuals can change from being one sex to another.
external fertilization
extranal fertilization happens when a female releases eggs outside of her body, and then those eggs get fertilized by sperm from a male in the outside environment, like in water.
internal fertilization
- Internal Fertilization: Sperm from a male goes into the female’s reproductive system, where fertilization happens.
2.Requirements: To do this, animals need behaviors and body parts that fit together for mating.
3.Timing and Signals: Successful fertilization depends on mating at the right time, signaled by environmental cues, chemicals, and courtship behavior.
Gamete Production & Delivery
- Sexual Reproduction: Animals need to make sex cells called gametes to reproduce sexually.
- Gonads: Most animals have organs called gonads that make gametes.
- Gamete Production: Some animals have simple systems where gametes form from basic tissue.
- Elaborate Systems: Other animals have complex systems with tubes and glands that carry, feed, and protect gametes and babies.
- Insects: Many insects have separate sexes with complicated reproductive parts.
- Spermatheca: Female insects often have a special place called a spermatheca to store sperm from mating.
what’s a Cloaca?
- Cloaca: It’s like a shared door in animals where poop, pee, and reproductive stuff come out from. It’s common in animals like birds and reptiles.
- Mammals: Most mammals have separate doors for poop and pee, unlike other animals. So, they don’t have a cloaca.
human reproduction
- Ovaries: They’re like special factories in the female body where eggs are made.
- Follicles: Inside the ovaries, there are small pockets called follicles. Each follicle has a baby egg inside, called an oocyte, and some helper cells around it.
- Ovum Development: Every month, one of these baby eggs grows up and becomes a mature egg, which we call an ovum. This process is called oogenesis.
ouvulation:
It’s when a mature egg is released from a little pocket called a follicle. Before the egg comes out, the follicle cells make a hormone called estradiol.
corpus luteum:
After the egg leaves, the empty pocket turns into a new structure called the corpus luteum. This mass makes hormones like estradiol and progesterone.
Hormones and Pregnancy:
These hormones help if a woman gets pregnant by keeping the womb ready. If there’s no pregnancy, the corpus luteum breaks down.
Oviduct or Fallopian Tube:
It’s like a tube that connects the ovary to the uterus, which is where a baby grows.
Cilia:
These are tiny hair-like structures in the tube that help move the egg from the ovary to the uterus.
Uterus or Womb:
It’s a special place where a baby can grow inside the body. The lining of the uterus, called the endometrium, has lots of blood vessels.
Cervix:
This is the lower part of the uterus that’s narrow and connects to the vagina, which is the opening outside the body.
vagina
is a thin-walled chamber that is the repository for sperm during copulation and serves as the birth canal
parts of the Vagina?
The vagina opens to the outside at the vulva, which consists of the labia majora, labia minora, hymen, and clitoris=(The clitoris has a head called a glans covered by the prepuce)
Blood Vessels and Nerve Endings of the vagina:
The vagina, labia minora, and clitoris have lots of tiny blood vessels, and the clitoris has many nerves, which make it sensitive to touch.
Mammary Glands
They’re not part of the reproductive system but are vital for mammal moms.
Milk Production: Inside these glands, small sacs make and release milk.
Male Anatomy
-
External Organs: These are the parts you can see outside the body, like:
the scrotum (where the testicles are) and the penis. -
Internal Organs: Inside, there are :
the gonads (testicles), which make sperm and hormones, and accessory glands that help with sperm and semen production.
Testes
These are the male gonads. They have coiled tubes where sperm form.
Sperm Formation:
Sperm are made in these tubes called seminiferous tubules.
Temperature and Sperm:
Sperm need lower temperatures to form properly.
Scrotum:
In many mammals, the testes are outside the body in a sack called the scrotum, where it’s cooler.
Sperm Movement:
Sperm develop in the seminiferous tubules within the testis and mature as they pass through the coiled tubes of the epididymis.
Ejaculation Process:
When a man ejaculates, sperm travel through two muscular tubes: the vas deferens and the ejaculatory duct. Finally, they exit the body through the penis via the urethra.
what is semen made of ?
Semen is a mixture of sperm and fluids from three groups of extra glands.
- Seminal Vesicles: These glands make most of the semen volume, about 60%.
- Prostate Gland: It adds its own fluid to the semen, which goes directly into the urethra.
- Bulbourethral Glands: These glands produce a clear liquid before ejaculation. It helps clear out any acidic urine in the urethra and prepares for the sperm to come out.
penis
- Penis Structure: The penis is made up of three spongy tubes that can fill with blood.
- Erection: When a person gets turned on, blood flows into these spongy tubes, making the penis bigger and harder.
- Sensitive Head: The tip of the penis has thinner skin and is very sensitive to touch.
Gametogenesis:
It’s the making of gametes, which are like special cells for making babies.
Spermatogenesis:
It’s the process of making sperm, and it happens all the time. Every day, millions of sperm are made, and it takes about 7 weeks for each sperm to fully develop.
Oogenesis:
This is how eggs are made, but it’s a slower process. Immature eggs start forming when a female is still an embryo, but they don’t finish growing until many years later, sometimes even decades.
product of Meiosis for spermatogenesis and oogenesis:
In spermatogenesis, all four cells from meiosis become sperm, but in oogenesis, only one of the four becomes an egg.
Timing:
Spermatogenesis happens all the time during teenage years and adulthood, while oogenesis starts early but takes a long time to finish.
continuous Production:
Sperm are made continuously without big breaks, but egg development has longer pauses.
Differences between Spermatogenesis and Oogenesis?
- All four products of meiosis develop into sperm, while only one of the four becomes an egg
- Spermatogenesis occurs throughout adolescence and adulthood
- Sperm are produced continuously without prolonged interruptions in oogenesis
How do hormones regulate sexual reproduction?
- Hormonal Control:
- Gonadotropin-releasing hormone (GnRH):
- FSH and LH:
human reproduction is coordinated by:
Hormonal Control: Reproduction in humans is controlled by hormones from three main parts: the hypothalamus, anterior pituitary gland, and gonads.
Gonadotropin-releasing hormone (GnRH):
This hormone comes from the hypothalamus and tells the pituitary gland to release two other hormones: FSH and LH.
FSH and LH:
These hormones from the pituitary gland regulate activities in the gonads (testes in males, ovaries in females) and help make sex hormones.
process of fertilization and Cleavage?
- Sperm penetrate the protective layer around the egg
- Receptors on the egg surface bind to molecules on the sperm surface
- Changes at the egg surface prevent polyspermy, the entry of multiple sperm nuclei into the egg
fertilization
is the formation of a diploid zygote from a haploid egg and sperm
Acrosomal reaction
(reaction to the process of fertilization.)
- triggered when the sperm meets the egg.
- the acrosome at the tip of the sperm releases hydrolytic enzymes that digest material surrounding the egg.
Acrosome
It’s a part at the tip of the sperm. It releases special enzymes that break down the stuff around the egg.
key parts to Cortical Reaction:
Cortical Reaction: This happens when the egg and sperm fuse.
- Vesicles Release: Right after the sperm attaches to the egg, tiny bags beneath its surface release their contents and form a barrier around the egg.
- Fertilization Envelope: This barrier blocks other sperm from getting in too fast.
- Calcium Ions: The cortical reaction needs a lot of calcium ions in the egg.
- Triggered by Calcium Change: A sudden change in calcium concentration triggers the cortical reaction.
- Spread of Calcium: When calcium spreads through the egg, it’s linked to the appearance of the fertilization envelope.
egg activation
- Calcium Increase: When calcium levels rise inside the egg, it speeds up processes like making energy and building proteins.
- Egg Activation: The egg becomes super active because of these quick changes in how it works.
- Pre-existing Proteins and mRNA: The egg already has all the stuff it needs for this activation.
- Sperm Fusion: The nucleus of the sperm combines with the nucleus of the egg, and the cell starts splitting into more cells.
Cleavage :
- Cleavage: After fertilization, the cell divides quickly without getting bigger.
- Blastomeres: This rapid division splits one big cell into lots of smaller ones, called blastomeres.
- Blastula: It’s a round cluster of cells with a hollow center filled with fluid called a blastocoel.
Cleavage patterns:
- Yolk Distribution: - Yolk, which stores nutrients, affects how cells divide.
- Animal and Vegetal Poles: - The top (animal pole) has less yolk, while the bottom (vegetal pole) has more yolk.
-
Appearance Differences:
-Because of this yolk difference, the top and bottom parts of the embryo look different. -
Cleavage Furrows:
-The first two splits make four equal-sized cells, but the third split is uneven, making some cells bigger than others.
Holoblastic cleavage
Holoblastic cleavage, the complete division of the egg, occurs in species whose eggs have little or moderate amounts of yolk,
For example, sea urchins and frogs.
Meroblastic cleavage
Meroblastic cleavage, incomplete division of the egg, occurs in species with yolk-rich eggs,
For example, reptiles and birds.
Morphogenesis
Morphogenesis, the process by which cells occupy their appropriate locations, involves:
- Gastrulation
- Organogenesis
Gastrulation
the movement of cells from the blastula surface to the interior of the embryo
Organogenesis
the formation of organs
What does Gastrulation do?
- rearranges the cells of a blastula into a three-layered (germ layers) embryo called a gastrula
- ectoderm
- endoderm
- mesoderm
ectoderm
forms the outer layer
Contributes to :
- epidermis
- nervous and sensory systems
- pituitary gland, adrenal medulla
- jaws and teeth
- Germ Cells
endoderm
lines the digestive tract
Contributes to :
- epithelial lining of digestive tract and associated organs ( liver, Pancreas)
- epithelial lining of respiratory, excretory, and reproductive tracts and ducts
- thymus, thyroid, and parathyroid glands
mesoderm
partly fills the space between the endoderm and ectoderm
contributes to:
-Contributes to :
- skeletal and muscular systems
- circulatory and lymphatic systems
- excretory and reproductive systems ( except germ cells)
- Dermis of skin
- Adrenal cortex
Process of sea urchins gastrulation:
Gastrulation starts at the vegetal pole of the blastula. Mesenchyme cells migrate into the blastocoel. The vegetal plate forms from the remaining cells and buckles inward through invagination. This forms the archenteron, which opens through the blastopore, eventually becoming the anus.
Process of frogs’ gastrulation:
In frog gastrulation, cells on the dorsal side of the blastula invaginate, forming a crease. The dorsal lip of the blastopore is above the crease. Involuting cells become endoderm and mesoderm, while surface cells form the ectoderm.
Process of Chickens gastrulation:
The embryo has two layers - the upper epiblast and the lower hypoblast. During gastrulation, the epiblast cells move towards the midline forming the primitive streak. The hypoblast cells contribute to the sac around the yolk but not the embryo itself.
human gastrulation
-The blastocyst is the human equivalent of the blastula and consists of the inner cell mass and the trophoblast.
-The trophoblast is the outer layer and initiates implantation.
-After implantation, the trophoblast expands and forms extraembryonic membranes that enclose specialized structures outside the embryo.
-Gastrulation involves the inward movement through a primitive streak.
Adaptations of Amniotes
1.The shelled egg of birds and other reptiles as well as monotremes (egg-laying mammals)
2. The shelled egg of birds and other reptiles as well as monotremes (egg-laying mammals)
amnion and amniotes
Embryos are protected by amnion fluid which allows reproduction on land. Mammals, reptiles and birds are known as amniotes for this reason.
The four extraembryonic membranes that form around the embryo:
-The chorion functions in gas exchange
- The amnion encloses the amniotic fluid
- The yolk sac encloses the yolk
- The allantois disposes of waste products and contributes to gas exchange
organogenesis
Organogenesis is the process where rudimentary organs develop from germ layers.
Notochord formation:
In early vertebrate organogenesis, the mesoderm forms the notochord.
Neural Plate Formation:
Ectoderm forms the neural plate in early vertebrate organogenesis.
Neural Tube Formation
The neural plate curves inward to form this structure.
Future of the Neural Tube
The neural tube will develop into this part of the body.
Development of Neural Crest Cells
These cells form various parts of the embryo along the neural tube.
Formation of Somites
Mesoderm lateral to the notochord forms these blocks.
Formation of Coelom
Lateral to the somites, mesoderm splits to create this body cavity.
Organogenesis in Invertebrates
mesoderm interacts with endoderm and ectoderm to give rise to the digestive tract, the heart and skeletal muscles, red blood cells, and the tubules of the kidneys, as well as a type of connective tissue called mesenchyme.
Differences in Body Plan
: For example, the neural tube develops differently in invertebrates, along the ventral side instead of dorsally like in vertebrates.
Morphogenesis in Animals vs. Plants
Movement of cells is involved in animals but not in plants.
Role of Cytoskeleton Reorganization
Changing cell shape during development is influenced by reorganization of the cytoskeleton.
Neurulation and Microtubules
In this process, microtubules aligned from dorsal to ventral help lengthen ectodermal cells along that axis.
Programmed Cell Death
It’s also known as apoptosis.
Alternative Term
Cells, groups, or tissues halt development and get engulfed by nearby cells.
Example: In embryos, more neurons are made than needed, so the extras are removed by apoptosis.
Determination
It’s when a cell or group commits to a specific fate.
Differentiation
This term refers to the resulting specialization in structure and function.
Genomic Sharing
Cells in a multicellular organism have this in common.
Gene Expression
Differences in cell types occur because of this process.
