Module 5.1 Flashcards
purpose of reproduction
continuity of species
Asexual reproduction
offspring are identical to single parent
Sexual reproduction
Union of gametes from two parents to form unique offspring
all organisms apart from bacteria and archaea have sexual reproduction
Binary fission
individual parent cell splits into 2
occurs in protists
Budding
new individual develops from some point on parent organism
occurs in:
animals
- jellyfish, anemone, coral, hydra
- sponges
- platyhelminths (flatworms
- tunicates
fungi
- yeast
protists
fragmentation/ regeneration
parent body fragments or splits and these parts develop into a fully grown identical individual
the fragments regenerate through mitosis and differentiation
Occurs in:
- sponges
- cnidarians
- platyhelminths
- Annelids
- echinoderms
longitudinal fission
Entire adult body splits lengthwise
occurs in sea anemones
Transverse fission
Planarians reproduce by ripping themselves into a head and tail piece that form new worms
Diploid cells
has two sets of chromosomes
Haploid cells
has 1 set of chromosomes
Parthenogenesis
development of unfertilised eggs into adults
occurs only in females
developed offspring may be haploid or diploid
resulting offspring may be identical to mother or mot, depends on diploidy and mechanism
may happen in changing conditions (lack of available mates)
may be part of normal life cycle
Sporulation
spores are tiny reproductive cells that are produced in great numbers by sporangia
spores are dispersed and travel great distance by wind
occurs in:
- fungi (moulds, mushrooms)
- Plants (ferns, mosses)
Asexual reproduction in fungi
changes arise in the genome due to sexual reproduction -> if well adapted to genome, it wants to conserve it
Sexual reproduction in fungi
if there is a change in environment new genetic material may have an advantage
reproduction in plants
all groups in kingdom plantae reproduce sexually, some can reproduce asexually
plants have a lifecycle that alternates between haploid and diploid
Groups of plants
Mosses and liverworts
ferns
gymnosperms (non-flowering plants)
Angiosperms (flowering plants)
Vegetative propagation
parts of parents detach and grow into new individuals
beneficial instable environments
includes:
- cuttings
- Stem modifications
- leaf modifications
is possible by meristem tissue
- commonly found in stems, leaves, tips of roots
- contains undifferentiated cells
Stem modifications
Stem modifications
- stolons -> long stems that grow along the surface (e.g., grasses)
- tubers -> swollen underground stems that store nutrients and can grow more plants e.g., potato
- rhizomes -> modified stems that typically grow horizontally underground -> roots and shoots grow at nodes in intervals of the rhizome and develop into new plants e.g., lilies, bamboo
- suckers -> new shoots arise from roots or underground stems, often after fires e.g., apples, blackberries
- artificial
cuttings
cuttings
- from stems, leaves, roots, petals (rare)
- artificial
leaf modifications
bulbs
- modified stem (a basal disc) that has fleshy leaves extending from it
- food storage for developing plants
- contains several buds of meristem tissue near the node where leaves are produced e.g., onions, garlic
natural
external fertilisation
occurs outside female body -> generally in water
- gametes exposed to many hazards
occurs mostly in marine invertebrates, fish and amphibians
Internal fertilisation
Sperm are deposited directly in (or onto) the female opening, using a penis or cloaca
fewer egg cells produced and kept protected inside the female body
fewer offspring are produced and kept protected inside the female body
occurs in:
- flat + round worms
- molluscs
- birds and mammals
- reptiles
animals can colonise land as they are not dependant on water for reproduction
Sexual reproduction in flowering plants
male gamete = pollen
female gamete = ovum inside the ovary
Pollination
A haploid male pollen grain lands on a female stigma
pollen grain grows tube that penetrates the stigma and carries sperm cells down to ovule
Seeds and fruits
fertilised ovule develops, protected within ovary
ovule containing embryo is termed a seed and the surrounding ovary grows to become a fruit
Internal vs external fertilisation
Advantages internal:
- reduces reliance on water for reproduction
- greater chance of offspring survival
Advantages external:
- many offspring can be produced
- wide dispersal of young
- is faster
- requires less energy
Disadvantages internal:
- fewer offspring produced
- requires more energy
- is slower
Disadvantages external:
- ‘hit and miss’ strategy with many wasted gametes
- often little to no parental care so few survive.
