Biology Test 298

Azolla, a water fern, forms a symbiotic association with the nitrogen-fixing cyanobacterium Anabaena azollae. This unique relationship allows Azolla to contribute significantly to the nitrogen content of rice paddies, where it is often used as a biofertilizer, enhancing soil fertility and reducing the need for synthetic fertilizers.

Pteridophytes, like ferns and horsetails, indeed require water for fertilization to occur. This is because their male gametes, or antherozoids, are motile and need a film of water to swim through to reach the female gametes housed within the archegonia. This dependency on water for fertilization is a characteristic feature of their life cycle and highlights the evolutionary transition from aquatic to terrestrial life.

Asexual reproduction occurs when an organism makes more of itself without exchanging genetic information with another organism through sex. This is beneficial to the population because genetically diverse populations have a higher chance of withstanding survival challenges such as disease and environmental changes.

Cycas is known for having the largest egg, sperm, and ovule among gymnosperms. This characteristic is part of what makes Cycas unique among gymnosperms, along with its pinnate leaves and slow growth rate. Cycas represents an ancient lineage of seed plants, providing insights into the evolution of gymnosperms.

In racemose type of inflorescence, the main axis continues to grow, and the flowers are borne laterally in an acropetal succession. This means that the oldest flowers are at the base and the youngest at the top, allowing continuous growth and flowering.

The use of scientific names eliminates confusion between nationalities that may have different common names for organisms by assigning them a universal name that acts as a code.

A flower is classified as actinomorphic when it can be divided into two equal halves in any radial plane passing through the centre. This type of symmetry, also known as radial symmetry, is common in flowers like mustard, Datura, and chilli.

A drupe is a type of fruit that develops from a monocarpellary superior ovary and is typically one-seeded. Examples include mango and coconut, where the pericarp is differentiated into an outer epicarp, a middle mesocarp, and an inner hard endocarp.

Red algae and cyanobacteria are non-motile.

Binomial nomenclature refers to the scientific naming system for organisms that uses two names: the genus name and the specific epithet. This system, developed by Carl Linnaeus, ensures that each species has a unique, universally accepted scientific name. The genus name is capitalized, and the specific epithet is lowercase, both italicized when typed or underlined when handwritten. An interesting additional fact is that this naming system provides a standardized way to identify organisms worldwide, facilitating communication and research across different languages and regions.