Unit 16 - Reproduction Flashcards
Asexual reproduction
The process resulting in the production of genetically identical offspring from one parent
Examples of organisms that can reproduce asexually
- Starfish
- Yeast
- Plants such as ferns
Advantages of asexual reproduction
- Only one parent is needed - saves time and energy
- Organisms reproduce very quickly - example bacteria can divide every 20 minutes
- Helps farming due to easy reproduction
Disadvantages of asexual reproduction
- All individuals have same characteristics
- Vulnerable to environmental changes
- One infection can spread to all
Sexual reproduction
The process involving the fusion of the nuclei of two specialized sex cells to form offspring
Male gamete
Sperm cell
Female gamete
Ovum/egg cell
Haploid
- The nucleus of a gamete
- Has 23 chromosomes
Diploid
- Nucleus of a zygote
- Has 46 chromosomes (23 pairs)
Advantages of sexual reproduction
- Introduces variation to the population
- More resistance to environmental changes and diseases
- Farmers making crops can choose the best characteristics from different strains to produce new plants
Disadvantages of sexual production
- A lot of time and energy is spent finding a mate and reproducing
- Much slower than asexual reproduction - months or years
Pollination
The transfer of pollen from the male part of a flower to the female part of another flower
Plants that rely on insects for pollination
Insect-pollinated
Male part of a plant
Stamen - anther & filament
Female part of a plant
Carpel - ovary, style & stigma
Sepal description & function
- Green part at the top of the stem under the petals
- Protects the flower when growing and helps to stop it from drying out
Petal description & function
- Brightly colored part of the flower
- Attract insects, birds or mammals for pollination
Stamen description & function
- Male part of the flower containing the filament and anther
- Produces male gametes (pollen) and provides needed structures and conditions for pollen transfer
Filament description & function
- There stalk that supports the anther
- Holds the anther in position to transfer pollen to a pollinator
Anther description & function
- Colored, usually with a powdery appearance
- Produces pollen grains which contain the plant’s male gametes
Stigma description & function
- Usually green and the tallest part inside the flower with a sticky layer
- Traps pollen from other flowers
Style description & function
- Thin structure that supports the stigma and is above the ovary
- Supports and presents the stigma in a position to receive pollen
Carpel description & function
- Female part of the flower that contains the stigma, style & ovary
- Produces female gametes and provides correct structures and conditions for fertilization
Ovary description & function
- Green, bulb-shaped part near the bottom of the flower
- Contains ovules (containing female gametes), which will develop into seeds after fertilization
Ovule description & function
- Structures within the ovary
- Female gametes are produced and contained in the ovules which will then become seeds upon fertilization
Pollen transported by insects
- Spiky outer layer
- Hooks onto insects
Pollen transported by wind
- Smaller, lighter & smoother than insect pollen
Self-pollination
The transfer of pollen grains from the anther of a flower to the stigma of the same flower or to a different flower of the same plant
Advantages of self-pollination
- Plants don’t have to rely on pollinators like insects
- Plants can grow where pollinators don’t exist
Disadvantages of self-pollination
- Reduces variation within the population
- Increases vulnerability to environmental changes and disease
Cross-pollination
The transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species
Advantages of cross-pollination
- Increases variation within the population
- Reduces vulnerability to environmental changes and disease
Disadvantages of cross-pollination
- Relies on pollinators to transport the pollen from one plant to another
Petals of wind-pollinated flowers
- Small and usually dull in color due to a lack of needing to attract insects
Petals of insect-pollinated flowers
- Large and brightly colored to attract insect pollinators
Anthers of wind-pollinated flowers
- Loosely attached and dance outside the flower so pollen can be blown by wind
Anthers of insect-pollinated flowers
- Located inside the flower to brush against insects
Stigma of a wind-pollinated flower
- Loosely attached and dangle outside the flower to catch wind-borne pollen - feathery
Stigma of a insect-pollinated flower
- Located inside the flower to brush against insects
Difference of nectar in insect & wind pollinated flowers
- Nectar is produced in insect-pollinated flowers but not in wind-pollinated flowers
Fertilization
When a pollen nucleus fuses with a nucleus in an ovule
How fertilization happens after pollination
- Pollen the grows through the style to the ovary
- Two male gametes move through the tube and reach an ovule
- One nucleus of the two sperm cells fuses with the egg cell
- Zygote forms and develops into an embryo
Germination
The process by which a plant grows from a seed
Needs of germination
- Water
- Oxygen
- A suitable temperature
Function of the testicles
Organ in which sperm cells and testosterone are produced
Function of the scrotum
A sack of skin that contains the testicles, helping to keep them at a slightly lower temperature than the rest of the body
Function of the prostate gland
Secretes fluid that nourished and protects sperm - mixture of liquid and sperm is semen
Function of the sperm duct
Muscular tube that connects the testicles to the urethra
Function of the urethra
Tube that allows the passage of semen and urine through the center of the penis
Function of the penis
During sexual intercourse, the penis is inserted into the vagina, allowing sperm to transfer into the female reproductive system
Function of the ovaries
To produce egg cells and the horses estrogen and progesterone
Function of the oviducts/fallopian tubes
Tubes connecting ovaries to the uterus, fertilization occurs here
Function of the uterus
Organ in which the embryo develops
Function of the cervix
Ring of muscle between the vagina and the uterus
Function of the vagina
Elastic muscular canal that a newborn passes through during childbirth & where a male’s penis is inserted in intercourse
Fertilization in humans
The fusion of the nucleus of a male gamete/sperm and the nucleus of a female gamete/egg to form a zygote
Structure of a sperm
- Three parts: head, midpiece, flagellum
Acrosome
- Tip of a sperm head
- Secretes digestive enzymes that allow the sperm to pass through the jelly coating of the surface of an egg cell
Flagellum
- Tail that lets the sperm cell move/propel the cell from one place to another
Midpiece of sperm
- Contains mitochondria
- Release energy by respiration to help keep the flagellum moving
Nucleus of an egg cell
- Contains the mother’s DNA which will fuse with the father’s
Cytoplasm of an egg cell
- Contains energy stores to allow the egg to survive several of days and to nourish the zygote if fertilization occurs into the implant in the wall of the uterus
Jelly coat of an egg cell
- Allows sperm to attach
- Creates a barrier from other sperm cells attaching one one has penetrated and entered the cell
Follicular cells of an egg cell
- Follicle cells attached to the egg to help nourish the egg in its journey
Size comparison of an egg and sperm cell
- Diameter of an egg cell is 0.1mm
- Diameter of a sperm cell is 0.05mm
Number comparison of egg and sperm cells
- Female usually releases only one egg cell each month
- Male can release 40M to 1.2B sperm in a single ejaculation
Motility comparison of egg and sperm cells
- Egg cells can’t move on their own
- Sperm cells can move 1-3mm an hour
Timing after fertilization before the embryo implants in the uterus wall
five days
Timing between how long it takes for an embryo to become a fetus
8 weeks
Function of the placenta
- Transfers substances from the mother to the fetus
- Transfers waste substances from the fetus to the mother so her body can excrete them
- Barrier against toxins and pathogens the mother is exposed to (except for nicotine and other pathogens)
Amniotic sac
- Protective layer for the fetus
- Full of amniotic fluid that contains nutrients needed by the fetus
Umbilical cord
Attached the fetus to the placenta
Exchange of materials between the fetus and placenta
- Placenta provides oxygen, carbohydrates, proteins, fats, vitamins, minerals and water to grow
- Fetus produces waste products such as carbon dioxide and urea
- Blood of mother diffuses through capillaries between the placenta and umbilical cord
Puberty
When a child’s body begins to change into an adult’s body
Surge of male sex hormone in puberty
Testosterone
Surge of female sex hormone in puberty
Estrogen
Changes during puberty for males
- Facial hair
- Shoulders get wider
- Voice deepens, voice box/Adam’s apple enlarges
- Hair under the arms
- Pubic hairs
- Penis and testicles grow larger
Changes during puberty for females
- Breasts start to develop
- Hair under the arms
- Pubic hairs
- Hip bones widen
Frequency of eggs cells being released from ovaries
- Once every 4 weeks (28 days)
- Or anything between 21-40 days
Ovulation
- When the egg is released from the follicle
- Happens around day 14
- After ovulation the follicle develops into corpus luteum
Lining of the uterus in the menstrual cycle
- From day 4 the lining of the uterus thickens so the egg can implant if fertilized
- If the egg is not fertilized the lining breaks down and is discharged as menstrual fluid (blood and other materials from the lining) - known as a period
Duration of a period
- Few days to a week
Four hormones in control of the menstrual cycle
- Follicle-stimulating hormone (FSH)
- Luteinising hormone (LH)
- Estrogen
- Progesterone
Where the four hormones of the menstrual cycle are secreted
- Estrogen - Ovary
- Progesterone - Corpus luteum in an ovary
- FSH & LH - Pituitary gland
Effect of FSH in the menstrual cycle
Causes an egg in an ovary to mature
Effect of LH in the menstrual cycle
Stimulates the release of a mature egg
Effect of estrogen & progesterone in the menstrual cycle
Involved in painting the lining of the uterus
How FSH interacts in the menstrual cycle
Stimulates the ovary to secrete estrogen
How estrogen & progesterone interact in the menstrual cycle
Inhibit the release of FSH & LH
How levels of the four menstrual cycle hormones change
- Start - progesterone is low - releases FSH
- FSH rises - causes egg to mature - stimulates release of estrogen
- Estrogen rises - releases FSH & later LH
- LH rises - releases the mature egg from its follicle at day 14
- Empty follicle become corpus luteum - progesterone produced
- Progesterone rises - Release of FSH & LH
Hormones during pregnancy
0 Corpus letup continues to release estrogen and progesterone until week around 8-12 weeks where placenta takes over production of hormones
Placenta function with hormone production
- Ensures no more eggs are released
- Maintains thick uterine lining to support growing fetus
- Prevents muscles of uterus from contracting
Examples of virus STIs
- Genital warts
- herpes
- HIV
STI
Sexually transmitted infection
Examples of bacterium STIs
- Chlamydia
- Gonorrhea
- Syphilis
Barrier methods for protection
Reduce the chance of coming into contact with infected body fluids
Examples of barrier methods
Female & male condoms
HIV
Human immunodeficiency virus
AIDS
Acquired immune deficiency syndrome