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.
