| what is binary fission | Binary fission is a form of asexual reproduction that occurs rapidly |
| how is DNA stored in prokaryotes | DNA in prokaryotes is not combined to histones
Circular chromosome is attached to cell membrane at a singular point called the origin |
| what is the origin | it is where a circular chromosome is attached to on a prokaryotes cellular membrane |
| what is a mesosome and what are its three main functions | Mesosome is a special membrane structure, which is formed by the extension of the plasma membrane into the cell in a prokaryotic cell. It helps in cell wall formation, DNA replication and distribution to daughter cells. |
| what are the four main steps of binary fission in prokaryotes | → DNA molecule is replicated
→ each strand of DNA is attached to a mesosome – fold of the membrane inside the cell
→ daughter chromosomes are separated as the membrane expands
→ plasma membrane and cell wall furrow inwards separating the cytoplasm resulting in two identical cells |
| how do plasmids replicate and what do they do | plasmids replicate independently of binary fission – plasmids have very few genes which give the cell extra survival value (many contain plasmids that make the cells immune to certain antibiotics) |
| define asexual reproduction | Production of one offspring from one parent – very simple |
| in what organisms does asexual reproduction occur in | Occurs in bacteria, fungi, many plants, and some animals |
| why do offspring from asexual reproduction not always look the same as their parents | While offspring from asexual reproduction are genetically identical, they may look different due to environmental factors |
| what is one downside and 2 advantages of asexual reproduction | -advantages - it is very fast and requires little energy
-disadvantages - Since they are genetically identical, and react the same to things, when there are environmental variations, they will either all die or all survive |
| what are the main types of asexual reproduction | fission, budding, fragmentation, spore formation, vegetative reproduction, and parthenogenesis |
| what is fission | most common asexual reproduction method in unicellular organisms such as protozoans, and bacteria
- It occurs when a parent cell divides in to two approximately equal parts |
| what are the three main types of fission | longitudinal fission (cell splits along its longest axis)
transverse fission (splits along its shortest axis)
strobilation (similar to transverse fission but occurs in multicellular organisms – a segment on the parent organism forms and once its matured it detaches and grows into its own organism) |
| what is budding | occurs in unicellular organisms such as yeast
→ similar to fission but division of cytoplasm is unequal
→ outgrowth or bud from parent detached to become new organism
→ budding also occurs in small multicellular organisms such as hydra |
| what is fragmentation | similar to fission but only occurs in multicellular organisms
→ an organism breaks in two and each piece regenerates missing elements to form a whole organism |
| what are some uses of fragmentation in horticulture | people use this in horticulture to retain advantageous properties a plant has – ideal properties are preserved from generation to generation |
| what organisms reproduce via fragmentation | common in flatworms, echinoderms, and marine worms |
| what is spore formation | can be both a form of sexual and asexual reproduction – usually only occurs in fungi
→ spores produced asexually are called mitospores and are produced via mitosis |
| what are mitospores | spores produced asexually
- the spores are covered in a protective coating allowing them to survive in unfavourable condition |
| what is sporangium | some fungi produce large amounts of spores inside a structure called a sporangium (sporangia – plural) – the spores are then disseminated after the sporangium wall disintegrates – the spores then germinate when they find suitable space |
| what structure do some fungi produce spores inside of | sporangium |
| what are spores called that are produced by budding | conidia |
| what are conidia | spores produced by budding are called conidia – they resemble dust, and they are not capable of movement |
| what is vegetative reproduction | many plants can reproduce asexually through vegetative propagation
- it is the growth of specialised tissue that can grow into a whole new plant when separated from its original parent plant |
| what is vegetative propagation | new plants are able to grow from seeds, cuttings, or other plant parts |
| what are the four types of plants that undergo vegetative reproduction | rhizomes, stolons, tubers and bulbs/corms |
| what are rhizomes | they reproduce via vegetative reproduction
- underground stems that branch off and give rise to new growths (ginger, couch grass and irises) |
| what are stolons | they are plants that reproduce via vegetative reproduction
- they have stems that branch off and give rise to new plants above ground
- strawberries and spider plants |
| what are tubers | they are plants that reproduce via vegetative reproduction
- swollen underground roots that have buds which can grow into new plants |
| what are bulbs and corms | they are plants that reproduce via vegetative reproduction
- produce lateral buds that develop into new plants (hyacinth bulbs, daffodils, and gladioli corms) |
| list one advantage and 2 disadvantages of reproducing via vegetative reproduction | → advantage - vegetative reproduction allows plant species to quickly overtake neighbouring plants which reproduce sexually (slower reproduction)
→ disadvantage - it can also cause competition for resource between parent and sister plants
→ disadvantage - the lack of genetic variations makes them vulnerable to disease and environmental changes |
| what is parthenogenesis | Parthenogenesis is an unusual form of asexual reproduction which occurs in some lizards, insects (bees, wasps, and ants), rotifers, and nematodes
→ it can only occur in females, and it involved the development of an egg without fertilisation |
| is there genetic variation in offspring produced via parthenogenesis | usually there is very little genetic variation, but in some species such as geckoes (some) genetic recombination can still occur |
| what is polyploidy | polyploidy is when you have more than 2 sets of chromosomes – for instance if a human had cells that were triploid (3n) |
| what is polyploidy usually caused by | this extra set of chromosomes is usually due to errors during meiosis |
| can humans have extra sets of chromosomes | humans will not survive to birth if they suffer from polyploidy (can if only some cells are polyploidy due to mistakes in meiosis) however many plants can survive due to their ability to reproduce asexually if they are triploid |
| how can polyploidy be induced in plants | polyploidy can be induced in plants using a chemical called colchicine (prevents formation of microtubules during cell division) |
| what is colchicine | chemical that prevents the formation of microtubules during cell division, hence inhibiting chromosomes from separating |
| what is one upside and downside of inducing polyploidy in plants | → advantage - polyploid plants are usually larger and grow faster – commonly used in agriculture for plants like spinach, turnips, apples, grapes, and watermelon
→ disadvantage - one downside is that these plants seeds tend to be less fertile |
