Reproduction Flashcards
reproductive success
determined by an organism’s ability to produce fertile offspring that survives to sexual maturity and productive offspring of their own
similarities between sexual and asexual organisms
- passes on DNA (method of heredity)
- produces offspring
- involves plants, fungi and animals
- form of reproduction
Differences between sexual and asexual organisms
Sexual
- two parents
- cells divide by meiosis
- genetic variation in offspring
- gametes produced
- generally, produces minimum of 1 offspring
- found in higher organisms (mammal)
Asexual
- one parent
- cells divide by mitosis, budding or fragmentation
- little chance of genetic variation
- no need to produce gametes
- generally, produces minimum of 2 offspring
- found in lower organisms
Pros of sexual reproduction
- speeds up evolution (options produced from variation drive evolution)
- high genetic variability (less susceptible to genetic disease . increases the genetic health of the species)
- facilitates adaptation: with variation there are options which can be better suited to the environment
Cons of sexual organisms
- energy costly: the process requires more energy to achieve the result
- courtship is time/resource consuming
- usually sacrifices the fitness of one sex to the other, can lead to death in the sacrifice of the fight to reproduce
Pros of asexual reproduction
- greatest increase in fitness for each individual (non-taxing on either sex)
- saves energy: the process requires less energy to achieve the result
- courtship is a non-issue: less time and resource consuming
Cons of asexual reproduction
- less genetic variability: highly susceptible to genetic disease decreasing the genetic health of the species
- adaptation to environments is difficult: with no variation there are a lack of suitable options
- inhibits adaptation: lack of options that can be better suited to changing environments
External and Internal Fertilisation: gametes
External:
larger number of gametes produced (male + female) as they are less likely to be fertilised
Internal:
less gametes are required because higher success rate (larger number of gametes produced from males)
Similarities: male and female gametes needed
External and internal fertilisation: union and conception mechanism
Ext:
- occurs in an aquatic environment
- simultaneous release of gametes (spawning events) regulated by environmental cues
Int:
- occurs inside the reproductive tract of the female (mostly on land)
- copulation
Similarities;
- sperm fertilise egg when they unite
- fertilisation when coming into close proximity - water environment required
External and internal fertilisation: chance of fertilisation, environment for zygote
External: - lower (gametes released in open area) - aquatic environment (vulnerable) Internal: - higher (confined space) - internal (protected environment)
External and internal fertilisation: Number of offspring, breeding frequency, parental investment
Ext:
- larger, many perish (small no. of offspring)
- more frequent (lower fertilisation rate)
- usually no parental investment
Int:
- smaler number - larger number survive
- less frequent - higher fertilisation rate
- parental care of eggs / developing young
Examples of External fertilisation
Bony fish: produces eggs (ova) in large batches where they fuse with sperm in spawning events.
Staghorn coral: Colony of invertebrate marine polyps which achieve fertilisation by shedding millions of gametes into the sea (these events being triggered and synchronised by environmental cues, such as water temperature, tides)
Internal fertilisation example
Reptiles: protects gametes from dehydration on land and other environmental stresses such as predation
Birds: most male birds do not have a penis (instead having a vent) so during copulation the male and females rub the opening to their cloaca for fertilisation.
Mammal:
Monotremes are oviparous (lay eggs after internal fertilisation)
Marsupials develop internally briefly then continue embryonic development in a pouch.
Placentals develop in a specialised organ of the uterus.
pollination
Transfer of the gametes from the male to the female
germination
the development of a plant from a seed or spore
fertilisation
when the pollen grain fuses with the ovule
process of plant reproduction
- Production of gametes occurs in the anther (male) and the stigma (female)
- Meiosis occurs, pollen and egg (haploid cells – gametes), followed by pollination
- Pollen tube delivers pollen to ovule in ovary (fertilisation)
- a pollen (gamete) is transferred to the stigma of a plant
- Pollen tube germinates and grows down the style (carrying inside it the pollen grain), delivering it to ovule in the ovary (fertilisation)
- Embryo (diploid cell) is produced and seeds start developing
- Seed dispersal occurs in order for the plant to colonise other area sand not be indirect competition with parent plant, followed by germination
Parts of a flower
male stamen: anther, filament
female pistil: stigma, style, ovary, ovule
- sepal (protects the bud)
- receptacle (where the flower grows)
asexual reproduction
- binary fission
- budding
- spores
- fragmentation and regeneration (vegetative propagation and animal regeneration)
Binary fission
Bacteria, protists, amoebae Unicellular organisms (i.e. bacteria has one chromosome)
Cell goes through the stages of mitosis; however, when it reaches cytokinesis it split into two different organisms. Newly formed cells are ‘clones’ of the parent and ‘parent identity’ is therefore lost.
Budding
Yeast, jellyfish, sea anemones
Occurs in unicellular and multicellular organisms.
A new organism (bud) grows off the original organism. As soon as the bud is capable of surviving on its own, it separates itself from the original organism. Only one daughter cell (which is smaller than the parent) is formed at a time (parent identity maintained)
Spores
Ferns, mosses, algae
Reproductive cell capable of developing into a new individual without fusion (fertilisation) with another reproductive cell.
Fragmentation and Regeneration: vegetative propagation
Natural:
Bulbs (onion, garlic, daffodil), Runners (strawberries, mint, grass), Rhizomes (irises, ginger), Tubers (potatoes)
Artificial:
cuttings, leaf stem or root
Fragmentation and regeneration: animal regeneration
starfish / earthworm
grafting
A technique used where a cutting is attached to another plant (called the new stock). The stock provides the root system and lower support for the new plant. Can be used for buds or parts of stems. Farmers use grafting to grow different kinds of fruit on existing trees. Example = rosebush, apple trees, other fruit trees
rhizome
Horizontal underground stems, with buds rising from these stems to the surface and growing into a new plant. Example = mint, iris, ginger, couch grass
tuber
Thickened underground stem bearing buds, from which new plants grow. Tubers contained stored food material. Example = potato, dahlia
runner
A stolon / runner is a stem that grows horizontally on the surface of the parent plant with a small terminal offspring. When the stolon breaks off, a new individual plant is formed. Example = strawberries, some grasses
bulbs
Formed from fleshy leaves which surround a small stem. This stem grows to become a new plant. Small bulbs may form around parent bulb. Example = daffodil, onion
corm
Swollen, solid stems, with the bases containing the stored food for the growing shoot. The bud grows from the swollen stem. Example = gladiolus, crocus
Oestrus cycle definition
development from haploid gametes to a fully formed foetus
process of pregnancy
- Gametogenesis occurs (cell enters meiosis) in the testes and ovaries
- Fertilisation is achieved through combining sperm cells with the egg cell (in fallopian tubes)
- Fertilised egg moves down the fallopian tube to the uterus, going through transitional stages
- Zygote: DNA combines giving the number of chromosomes (46)
- Blastocyst: bundle of cells
- Development of the utero lining is important in order for the blastocyte to implant
mammal types: monotremes
lay eggs
mammal types: marsupials
develop a pouch that allows for protection
mammal types: placental
internal development and fertilisation, providing increased protection from environmental stresses and allowing a constant supply of nutrients via placenta (energy consuming)
seasonal breeders
- hormones regulated fertility - limited to certain periods of time within the year (during oestrus)
- young born in favourable conditions (resources, temperature) = increased survival
- reduced mating time
- gestation and rearing young takes place (most vulnerable to predators and energy drain)
continuous breeders
- Female fertility occurs in a cycle that repeats throughout the year. Sexual activity throughout the year.
- Typically higher order primates (and some other mammals – pigs, mice, rabbits)
- can breed all year round (no restrictions and greater number of offspring)
gonotrophic hormones
definition: hormones which acts an on gonads (organ that produces gametes)
- follicle stimulating hormone
- luteinising hormones
gonotrophic hormones female
FSH:
- Causes an egg to mature in an ovary
- Stimulates the ovaries to release oestrogen 14 days into cycle
LH
- anterior pituitary gland sends a spike of LH to signal for the release of the egg (ovulation)
gonotrophic hormones male
FSH:
- Stimulates production of a protein in Sertoli cells (in testes) which maintains testosterone levels that achieve spermatogenesis)
LH:
- Stimulates the production of testosterone in the testes (Leydig cells)
sex hormones:
produced by a sex gland
Female: progesterone
- Maintains the lining of the uterus during pregnancy – if an egg is fertilised the body produces this to ensure the process is not restarted
- Released from the corpus luteum
- Blocks the release of FSH and LH so that further ovulation does not occur during pregnancy
Female: oestrogen
- Prepares the lining of the uterus for implantation, role in feedback control
- Secondary sexual characteristics, enlarged breasts, pubic hair, widening of hips
Male: androgen
- T is produced in response to LH
- Has a regulatory affect as it inhibits the action of GnRH
- Produced in Leydig
Male: inhibin
- Produced by Sertoli cells, travels to pituitary gland
- Inhibits production of LH and FSH
gnrh
GnRH = gonadotrophic releasing hormone
- Produced in hypothalamus, moves to anterior pituitary gland
- Stimulates the production of LH and FSH
Process: female oestrus cycle
- GnRH (gonadotrophic releasing hormone) produced in hypothalamus moves to anterior pituitary gland – stimulating the production of FSH and LH.
- FSH (follicle stimulating hormone) is secreted by the pituitary gland and begins the development of an egg in the ovary.
- The FSH stimulates the release of oestrogen from ovaries to prepare the lining of the uterus for implantation. Blocks the production of FSH and LH hormone.
- A spike in LH (luteinizing hormone) from the pituitary gland signals for the release of the egg from the ovaries (ovulation).
- The egg travels to the fallopian tubes and if fertilisation occurs, the body maintains pregnancy through the secretion of progesterone which maintains the lining, stopping menstruation from occurring through inhibiting production of FSH.
Process: female - fertilisation and implantation
- The egg releases chemicals which attract the sperm.
- The oviduct secretes a fluid that travels down the female reproductive tract. The sperm swim through the fluid (upstream = positive rheotaxis).
- Sperm that reach the oviduct (site of fertilisation) are held in storage and released in small batches.
- Presence of progesterone and alkaline pH causes sperm to mature so it can penetrate the egg. The sperm becomes hypermobile – the tail beats strongly so the sperm can propel into egg.
- The sperm physically push through the first outer membrane (corona radiata) which is made of protective cells and releases enzymes to assist penetration.
- Acrosome (protective cap) of sperm gets through to the next barrier – zone pellucida. The acrosome fuses with cell membrane and the tip of sperm releases more enzymes.
- Surface proteins allow one sperm to penetrate this barrier – triggering the release of enzymes by the egg that destroy the glycoproteins in the zona pellucida, causing electrical charges which prevent other sperm from entering.
- A zygote is produced embryo blastocyst foetus
Process: male
- GnRH (gonadotrophic releasing hormone) produced in hypothalamus moves to anterior PG, stimulating the production of FSH and LH.
- LH stimulates the production of testosterone in the testes (Leydig cells)
- FSH stimulates the production of a protein by Sertoli cells in the testes, maintains testosterone levels high enough to produce spermatogenesis.
- Testosterone inhibits the action of GnRH produced by hypothalamus and allow for spermatogenesis.
- Inhibin inhibits the production of LH and FSH in pituitary gland.
hormones and birth development: prostaglandins (PG)
progesterone
- Makes the tissue of the uterus more sensitive to OT
hormones and birth development: oxytocin
- Stimulated by PG
- Triggers and maintains labour causing muscular contractions of uterus to increase as pressure of the baby’s head onto cervix increases
- Causes placenta to release prostaglandins
- Lactation
- Initiates labour: muscles in the uterus contact and tissue of cervix softens so the cervix can dilate (widen)
- Positive feedback on PG and on pituitary to make more OT
hormones and birth development: prolactin
- Stimulated by OT
- Secreted by pituitary gland
- Enlargement of mammary glands for milk production
hormones and birth development: relaxin
- Ovaries: helps dilate cervix to allow passage of foetus; widens pubic bones and relaxes pelvic ligaments
hormones and birth development: progesterone
- Produced by the corpus luteum and then placenta: maintains endometrium, causes decrease in GnRH, FSH and LH, stimulates changes in the mother’s body
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insulin
foetal pancreas, from 10 weeks
human chorionic gonadotropin (hcG)
developing embryo, first trimester
