Biology: Plant Reproduction, Evolution, and Microorganisms

Fertilization

Restores diploidy (2n) by combining gametes.

Meiosis

Restores haploidy (n) by producing gametes or spores.

Analogous features

Traits that are examples of convergent evolution, not shared ancestry.

Diploid zygote

Formed by fertilization, leading to the sporophyte stage.

Haploid spores

Produced by meiosis, leading to the gametophyte stage.

Molecular sequences

Preferred in modern taxonomy as they provide objective evidence of evolutionary relationships.

Synapomorphies

Shared derived traits that indicate common ancestry within a group.

Cyanobacterial blooms

Caused by excess nutrients leading to explosive growth and oxygen depletion.

Chemoautotroph

A bacterium that gains energy from inorganic chemicals instead of light or organic carbon.

Heterocysts

Adaptation in cyanobacteria that protects nitrogenase, allowing nitrogen fixation in low oxygen.

Indicator species

Cyanobacteria that signal water quality changes through rapid pigment and growth response.

Coenocytic hyphae

Characteristic of Zygomycota, which reproduces sexually through zygosporangium formation.

Nutrient cycling

Fungi decompose organic matter, releasing nutrients back into the soil.

Mycorrhizae

Mutualistic association where fungi increase water/mineral absorption and plants supply sugars.

Antibiotics like penicillin

Produced by fungi to outcompete bacteria by inhibiting their growth.

Lichens

Important in primary succession as they break down rock and create soil.

Yeasts

Produce CO₂ anaerobically from fermentation, converting sugars to ethanol and energy.

Red algae

They have phycoerythrin pigments that absorb blue/green light, which penetrates deeper water.

Dinoflagellates

Rapid population growth (bloom) and specialized enzymes that produce light under stress or movement.

Fucoxanthin

Shallow to mid-depth marine zones; belongs to brown algae (Phaeophyceae).

Agar or carrageenan

Both polysaccharides with commercial and ecological importance.

Green algae

They share chlorophylls a/b, cellulose cell walls, starch storage, and similar life cycle patterns.

Bryophyte

Water is required for sperm motility during fertilization.

Vascular tissue

Allowed transport of water/nutrients and structural support, enabling taller, drier habitats.

Sporophyte dominance in ferns

Sporophytes are diploid, reducing mutation risk and allowing wider spore dispersal.

Heterospory

Produces separate micro- and megaspores → precursors to pollen and ovules in seed plants.

Sori

Clusters of sporangia on fern fronds' undersides, where meiosis produces spores.

Mosses

Store carbon in peat, prevent erosion, and retain moisture.

Whisk ferns and horsetails

Whisk ferns lack true leaves/roots; horsetails have jointed stems with silica — both show early vascular adaptations.

Cyanobacteria, fungi, and mosses

Cyanobacteria (no alternation) → fungi (haploid-dominant) → mosses (alternation of generations).

Fungi and plants

Fungi with roots (mycorrhizae) for nutrient trade; plants with animals or microbes for pollination or defense.

Haploid-dominant life cycle

Among bryophytes — early non-vascular land plants.

Reproductive adaptations

Need to prevent desiccation and dependence on water → development of pollen, seeds, and protective gametangia.

Green organism with chlorophyll a/b

Likely belongs to green algae (Chlorophyta/Charophyta) — precursor group to land plants.