Reproduction Flashcards
Purpose of reproduction
“To produce new organisms similar to themselves
Two types of reproduction
“Asexual and sexual.”
Key events in sexual reproduction
“Meiosis and fertilization.”
Meiosis’s role
“Halves the number of chromosome sets (2n to n) to produce haploid cells/gametes.”
Fertilization’s role
“Combines chromosomes from two haploid gametes to form a diploid (2n) zygote.”
Needs of sexual reproduction
“Gonads
Prevalence of sexual reproduction
“Common in most organisms
Sexual reproduction in hermaphrodites
“Involves gametes from separate individuals.”
Genetic variation in sexual reproduction
“Introduced during meiosis and fertilization.”
Crossing over
“Occurs between chromatids of homologous chromosomes during meiosis.”
Independent assortment
“Homologous chromosomes separate independently during the first nuclear division of meiosis.”
Result of meiosis
“Gametes with different genetic makeup.”
Result of fertilization
“Genetically unique zygote formed from fusion of gametes from two individuals.”
Importance of genetic variation
“Adaptation to environment
Overall importance of sexual reproduction
“Contributes to species survival and continuation of life.”
Vertebrate sexual reproduction
“Involves haploid gamete formation (meiosis)
Vertebrate sex separation
“Individuals are male or female
Vertebrate reproductive strategies
“Range from external fertilization to viviparity
Fertilization in fishes and amphibians
“External
Parental care in fishes and amphibians
“Most do not look after their young.”
Fish eggs
“Numerous
Amphibian eggs
“Many
Amphibian larvae
“Actively feed and develop before becoming adults.”
Wastage in fish and amphibian reproduction
“High
Reptile, bird, and mammal fertilization
“Internal
Adaptations for internal fertilization
“Specialized organs to bring sperm and egg together inside the female.”
Advantages of internal fertilization
“Safer environment for gametes
Amniote egg
“Laid by reptiles and birds
Reptile egg laying
“Eggs laid in crevices or buried in sand
Bird egg laying
“Eggs laid in nests
Mammalian embryo development
“Embryo retained and nourished within the female’s uterus via the placenta.”
Mammalian egg
“Small amount of yolk
Amnion function in mammals
“Fluid-filled sac protecting the embryo.”
Placenta formation
“Embryo’s part from allantois and chorion
Mammalian parental care
“Young born live
Efficiency of reproduction in birds and mammals
“High
Flowering plant reproduction
“Most are bisexual
Products of meiosis in flowering plants
“Haploid spores (not gametes) that produce haploid gametophytes (pollen grain and embryo sac) through mitosis.”
Gametophyte
“Haploid structure (pollen grain/embryo sac) that produces gametes.”
Process after gamete fusion in flowering plants
“Diploid zygote formed
Seed function
“Contains food store for embryo
Seed germination
“Seed germinates and grows into a new plant (sporophyte).”
Plant sexual life cycle
“Alternation of haploid gametophyte and diploid sporophyte generations.”
Plant gametophytes
“Reduced
Plant Pollination
“External agents carry male gametes (in pollen) to where the eggs are.”
Plant Male Gametes
“Non-motile
Adaptation in Flowering plants
“Flowering plants do not need water to transport their male gametes”
Fertilization Uniqueness in Flowering Plants
“A pollen grain produces two male gametes”
Double Fertilization
“One male gamete fertilizes the egg (forms zygote)
Seed Development
“Zygote grows into a seed without needing water.”
Seed Germination Requirement
“Needs to absorb water to germinate and develop into a young plant”
Vertebrate reproductive system
“Consists of gonads
Gonads Function
“Produce gametes and hormones for reproduction.”
Types of Gonads
“Testes (male
Reproductive ducts and glands function
“Store/transfer gametes
Urinogenital system
“Excretory and reproductive systems represented together (ducts drain into urine-carrying ducts).”
Cloaca
“Cavity where alimentary
Sperm-transfer organ
“Males of mammals
External genitals
“Parts of the reproductive system seen externally.”
Importance of external genitals
“Help identify male and female mammals.”
Human male external genitals
“Scrotal sacs and penis.”
Testes location
“Lower abdomen in young males
Scrotum function
“Sac outside the body that keeps testes at a temperature slightly below body temperature for sperm production”
Testis structure
“Hundreds of compartments with seminiferous tubules.”
Seminiferous tubules function
“Produce sperms.”
Epididymis
“6m long coiled tubule outside each testis
Sperm duct/vas deferens
“Muscular tube that carries sperm from the epididymis.”
Urethra (male)
“Muscular tube through the penis
Accessory glands
“Seminal vesicles
Seminal fluid
“Secretions from accessory glands
Semen
“Milky fluid
Penis function
“Conveys urine and semen
Penis structure
“Cylindrical organ with erectile tissue
Erection
“Blood pumped into erectile tissue
Glans penis
“Sensitive region at the tip of the penis
Foreskin/prepuce
“Retractible skin covering the glans penis.”
Circumcision
“Surgical removal of foreskin.”
Sperm production timing (human)
“Begins at puberty
Sperm production rate (human)
“About 300 million daily.”
Sperm production site
“Seminiferous tubules.”
Spermatogenesis
“Cells in seminiferous tubules undergo meiosis to form spermatids
Sperm storage
“Epididymis.”
Sperm viability
“Mature sperms can remain viable in sperm ducts for up to three months.”
Sperm structure
“Head (nucleus
Acrosome
“Sac at the sperm head tip
Sperm motility
“Tail movements
Hormonal control of male sexual activity
“Pituitary gonadotropins regulate testes function.”
Testosterone
“Male sex hormone
Human female urinary/reproductive passages
“Separate and open separately to the exterior.”
Vulva
“Female external genitals.”
Vulva components
“Folds of skin surrounding openings
Clitoris
“Erectile
Ovaries
“Female gonads
Oviduct/Fallopian tube
“Tube with a funnel-shaped opening near each ovary.”
Fimbriae
“Muscular finger-like structures with cilia that waft ova into the oviduct.”
Oviducts
“Narrow spiraling tubes with muscular walls lined with mucus-secreting cells
Uterus/womb
“Muscular organ with endometrium lining.”
Endometrium
“Mucous membrane lining the uterus.”
Cervix
“Ring of muscles connecting the uterus to the vagina.”
Vagina
“Muscular tube leading from the cervix to the outside.”
Hymen
“Fold of connective tissue at the entrance of the vagina (may be present).”
Number of offspring (human)
“Usually one at a time.”
Uteri (other mammals)
“Some mammals have two uteri that unite to lead into the vagina.”
Vestibule
“Common urinogenital passage in some mammals (e.g. rabbit).”
Primary oocytes
“Potential egg cells in ovaries at birth (about 200
Mature ova development
“400-500 develop during a female’s reproductive life (puberty to menopause).”
Menstrual cycle events
“Ovum maturation
Menstrual cycle length
“28 days.”
Menstrual cycle control
“Hormones ensure uterus is ready for fertilized ovum.”
Follicle development
“Primary oocyte surrounded by granular cells
Graafian follicle
“Mature follicle with fluid and secondary oocyte
Ovulation
“Release of ovum from ovary
Ovum coverings
“Zona pellucida (protein coat) and layer of granular cells.”
Ovum transport
“Waited into oviduct
Corpus luteum
“Ruptured Graafian follicle develops into corpus luteum
Corpus luteum fate
“If no fertilization
Menstrual flow
“Sloughing of extra uterine endometrial tissue and some blood
Endometrium rebuilding
“Oestrogen causes cells of the endometrium to divide rapidly
Endometrium maintenance
“Secretion of mucus maintains the endometrium in an optimal state for the implanting of an embryo.”
Sexual cycle in most other mammals
“The sexual cycle does not occur monthly but rather at specific times of the year.”
Oestrous cycle
“Most mammals have an oestrous cycle rather than a menstrual cycle.”
Differences between the oestrous and menstrual cycle
“The main difference is that in the oestrous cycle
Oestrous and behavioural changes
“In most mammals
Hormonal control of female sexual activity
“The female sexual cycle is controlled by several hormones.”
Pituitary gonadotropins in females
“At puberty
FSH function in females
“FSH stimulates the development of the Graafian follicle.”
Oestrogen function
“Oestrogen
Oestrogen functions
“Stimulates the repair and thickening of the endometrium
LH function
“LH brings about ovulation and the development of the corpus luteum.”
Progesterone function
“Progesterone
Hormone levels if fertilization occurs
“If fertilization and implantation occur
Placental hormone
“The placenta also secretes a hormone (progesterone) that takes over the function of the corpus luteum.”
Hormone levels if fertilization does not occur
“If fertilization does not occur
Result of falling hormone levels
“This results in the breakdown of the endometrium and the start of a new cycle.”
Pregnancy
“Pregnancy or gestation is the period from fertilization to birth.”
Fertilization site
“In humans
Fertilization process
“Only one sperm penetrates the egg cell membrane and fertilizes the egg.”
Egg changes after fertilization
“After fertilization
Zygote formation
“The nuclei of the sperm and egg then fuse to form a zygote.”
Cleavage
“The zygote undergoes a series of mitotic divisions as it passes down the oviduct to form a solid ball of cells
Blastocyst formation
“The morula develops into a hollow ball of cells
Implantation
“The blastocyst becomes embedded in the endometrium about seven days after fertilization.”
Placenta development
“The placenta develops from both embryonic and maternal tissues.”
Placenta functions
“It is the organ of gaseous exchange
Placental hormones
“The placenta also secretes progesterone and oestrogen which maintain the endometrium and prevent the occurrence of a new cycle.”
Gestation period
“The length of time the embryo develops in the uterus varies from species to species.”
Human gestation period
“In humans
Embryonic development
“During the first three months (first trimester)
Organogenesis
“All the main organs are formed during this period.”
Fetal development
“After three months
Birth (parturition)
“At the end of the gestation period
Birth process
“The uterus undergoes strong muscular contractions (labour) to expel the baby through the vagina.”
Amnion’s role in birth
“The amnion bursts and its fluid (amniotic fluid) lubricates the birth canal.”
Placenta and umbilical cord after birth
“The placenta and umbilical cord are expelled as the afterbirth.”
Lactation
“After birth
Milk composition
“Milk is a rich fluid containing all the necessary nutrients for the growth of the young.”
Hormonal control of lactation
“Milk production is under hormonal control.”
Placental hormones and milk production
“The high levels of progesterone and oestrogen produced by the placenta during pregnancy inhibit milk production.”
Prolactin and milk production
“After birth
Oxytocin and milk release
“Suckling by the baby stimulates the release of oxytocin from the pituitary gland
Contraception
“Contraception is the prevention of pregnancy.”
Natural methods of contraception
“These methods involve no special devices and are based on the woman’s menstrual cycle.”
Rhythm method
“The rhythm method involves avoiding sexual intercourse during the fertile period
Fertile period
“The fertile period is about two days before and two days after ovulation.”
Temperature method
“The temperature method involves taking the woman’s temperature daily.”
Temperature and ovulation
“There is a slight rise in temperature (about 0.5°C) at ovulation.”
Withdrawal method
“The withdrawal method involves the man withdrawing his penis from the vagina before ejaculation.”
Effectiveness of natural methods
“These natural methods are not very reliable.”
Barrier methods of contraception
“These methods prevent the sperm from reaching the egg.”
Condom
“The condom is a rubber sheath that is placed over the penis before intercourse.”
Diaphragm
“The diaphragm is a rubber cap that is placed over the cervix.”
Spermicides
“Spermicides are chemicals that kill sperm.”
Effectiveness of barrier methods
“Barrier methods are more reliable than natural methods
Intrauterine device (IUD)
“The IUD is a small plastic or metal device that is inserted into the uterus by a doctor.”
IUD action
“The IUD prevents implantation of the fertilized egg.”
Hormonal methods of contraception
“These methods use hormones to prevent ovulation or implantation.”
Oral contraceptives (the pill)
“Oral contraceptives contain synthetic progesterone and oestrogen.”
Pill action
“The pill prevents ovulation by inhibiting the release of FSH and LH.”
Mini-pill
“The mini-pill contains only progesterone.”
Injectable contraceptives
“Injectable contraceptives contain progesterone and are given every three months.”
Implantable contraceptives
“Implantable contraceptives are small rods that are inserted under the skin and release progesterone.”
Morning-after pill
“The morning-after pill contains a high dose of progesterone and can prevent pregnancy if taken within 72 hours of unprotected intercourse.”
Surgical methods of contraception
“These methods are permanent and involve surgery.”
Vasectomy
“Vasectomy involves cutting and tying the sperm ducts.”
Tubal ligation
“Tubal ligation involves cutting and tying the fallopian tubes.”
Infertility
“Infertility is the inability to conceive after one year of regular unprotected intercourse.”
Causes of infertility
“Infertility can be caused by a variety of factors
Treatment of infertility
“Infertility can be treated with a variety of methods
Assisted reproductive technologies (ART)
“ART includes methods such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).”
In vitro fertilization (IVF)
“IVF involves fertilizing eggs with sperm in a laboratory dish and then transferring the resulting embryos into the uterus.”
Intracytoplasmic sperm injection (ICSI)
“ICSI involves injecting a single sperm directly into an egg.”
Reproductive behaviour
“Reproductive behaviour is any behaviour that increases the chances of fertilization.”
Types of reproductive behaviour
“Reproductive behaviour can include courtship
Courtship
“Courtship is the behaviour that precedes mating.”
Purpose of courtship
“Courtship helps to ensure that individuals of the same species mate and that the female is receptive to mating.”
Courtship signals
“Courtship can involve a variety of signals
Mating
“Mating is the act of copulation or insemination.”
Parental care
“Parental care is any behaviour that increases the survival of offspring.”
Forms of parental care
“Parental care can include nest building
Evolutionary significance of reproductive behaviour
“Reproductive behaviour is important for the survival of the species.”
