Biology exam notes: Units on reproduction in plants and animals (sexual & assexual), mitosis & meiosis, growth and cell division

BIOLOGY TERM 3

Reproduction

Asexual reproduction

·leads to the production of offspring that are very like their parents and so carry on adaptations to the conditions they live in.

·Does not depend on the production of specialised reproductive cells (gametes)

·Does not depend on the chance meeting of sperm and egg, eg. Aquatic species shed their gametes into the water.

·Does not depend on two mature individuals, one to produce sperm and the other to produce eggs, coming together at an appropriate time for the transfer of sperm.

Fission

·of a single-celled organism is the simplest type of reproduction.

·A cell divides across a midsection to form two equal daughter cells. Eg. Most bacteria and some unicellular algae and fungi.

Budding

·A small part, including a nucleus produced by mitosis, pushes out from the parent cell and breaks off.

·Occurs in yeasts.

Spores

·Are the reproductive cells of single-celled and multicellular algae and fungi.

Babesia LifeCycle(French version)

Uterus and uterine tubes.

Histology

·The spores of aquatic fungi and algae swim through water by using their long whip like flagella.

· Currents of air disperse microscopic spores of terrestrial algae and fungi. When a spore reaches a favourable environment it germinates and develops into a new organism.

Fragmentation and Regeneration

·Fragmentation (the breaking off of parts of the parent body) followed by regeneration (the growth of detached part into a new individual) is a form of asexual reproduction that occurs in some multicellular organisms.

·A many celled structure that is capable of growing into a whole new individual detaches from the parent, either by a special mechanism or by accident.

·Quite frequently fragmentation is a result of damage.

·Repair after fragmentation can become reproduction in organisms such as starfish and earthworms. Eg. Propagation of plants.

Parthenogenesis

·is the development of an unfertilised egg into an embryo. Eg. Plants, honey...