5.1. Part 2 - Bacteria, Protist, Fungi Flashcards
Binary fission
- When a cell becomes too big, its surface area is not capable of meeting needs of nutrient absorption and water removal.
- Therefore it divides. The cell elongates, and DNA is duplicated. Duplicated DNA moves to different sides of the cell, then cytokinesis occurs, splitting the cell into two daughter cells.
- Used by bacteria and protists
NOT the same as mitosis. Mitosis is the process by which the nucleus divides in eukaryotes. Bacteria are prokaryotes - they do not have a nucleus, so DNA replication and cell division is NOT a form of mitosis
Sexual reproduction in bacteria
- Special conditions: not enough nutrients to grow in volume and divide.
- Bacteria comes in contact, bridge like structure is formed and genetic material is transferred. As there is a double of genetic material, binary fission follows
- This increases probability of survival as there is genetic diversity.
- Internal fertilisation
Assess the pro/con of binary fission in bacteria
Advantages:
* Rapid
* Only requires one organism to produce offspring and increase the population
Dis
* Lack of genetic diversity
* But high rates of mutations during DNA replication
Protists reproduction
Divide by binary fission and budding (both asexual)
Binary fission - e.g. amoeba
* Protist body is pinched into two parts/halves
Budding - e.g. protozoa
* Rarely.
* The nucleus divides, DNA replications occurs many times by mitosis
* There are many copies of DNA.
* The new nuclei move into the buds and then separate, taking some cytoplasm with them
Sexual - only very rare circumstances
* Genetic material divides into daughter cells, and the haploid cells fuse to form a new protists with a new combination of genes.
Protists and fungi are eukaryotic, so we can say that the process by which they replicate the nucleus is called mitosis
Protist reproduction methods pro/con
Advantages
* Ability to sexually reproduce provides evolutionary advantage (greater variation)
* Easy divide (fast and little energy) and growth of population in asexual
Disadvantages
* Asexual reproduction does not result in variation or adaptations.
Fungal reproduction
Asexual and sexual, closely related to plants and animals.
Asexually: spores
* Single celled reproductive units are released and carried by abiotic factors (wind, water). They are haploid, and do not require other cells to reproduce.
* Spores begin to grow when reaching favourable conditions. Germinate and grow into a new haploid fungi
Asexually: budding. E.g. yeast
* DNA replicates and moves to sides of the organisms. Buds are formed which separate from the main body and form new organisms.
Asexually: fragmentation E.g. Penicillium
* Part of the fungus can spread and develop apart from the colony, forming new colonies.
Sexual: E.g. black bread mould. It varies between fungi
* Two haploid cells fuse to form a diploid cell. Meiosis occurs to form haploid spores.
* These spores form haploid fungi, resulting in genetic diversity.
Fungi asexual reproduction pro/con
Advantage
* Spores are easy to spread, no requirement of other spores to reproduce
* Can easily find optimum environment
* Limited energy required
Disadvantage
* Limited variation - cannot survive rapid changes of environment
Compare sexual and asexual reproduction
Sexual
* Two parents
* Genetic variation
* Requires uniting of gamete
* Low number of offspring with significant energy input
* Humans, angiosperms
Asexual
* One parent
* No genetic variation
* Typically do not require uniting of gametes
* High number of offspring with low energy input
* Bacteria, grasses, protist, fungi
Asexual reproduction benefits in Australian environment.
It is beneficial in harsh conditions that make it difficult to acquire energy for sexual reproduction and find mates.
- Arid areas, high temperatures, low nutrients
- Easy spread by asexual reproduction. E.g. spinifex grass
- Difficult to find mates - Parthenogensis e.g. geckos.
- Beneficial after bushfires. E.g. colony wattle repopulate burnt areas through asexual reproduction
Fungi sexual reproduction pro/con
Pro:
- More genetic variation in offspring → resilience
- Combination of sexual and asexual methods means that fungi can choose when and how to propagate, maximising chances of species continuity
Cons:
- Sexual reproduction requires two spores of different mating type
Hyphae
Tiny branching filaments that spread through material on which a fungus feeds, such as soil. Multicellular fungi grow as hyphae
- Most hyphae have haploid nuclei for most of their life cycle.
Mycelium
Interwoven mass of hyphae. Fungus often grows as a mycelium
Origin of replication (bacteria binary fission)
- Bacteria have 1 chromosome which is a long, circular DNA molecule
- DNA molecule has a region called the origin of replication, which is where DNA replication begins
- After DNA has been duplicated, each copy moves to opposite sides of the cell and cytokinesis occurs
Budding vs binary fission size comparison
Size of daughter cell in relation to parent cell
Budding: parent cell > newly formed bud
Binary fission: parent cell = daughter cell
