Master of Orion II: Battle at Antares/Biology

The Biology techs appear in the 3rd row of the right column in the Research Menu.

0 RP: Starting techs
None. You have to research all Biology techs in pre-Warp games.

80 RP: Astro Biology
Fully-automated Building that increases a colony's food production by 2 without needing any farmers. Its main advantage is that its output is not reduced by blockades. Like most farming techs, Hydroponic Farm cannot be researched by Lithovores. Building that increases a colony's maximum population by 2.
 * Hydroponic Farm (60 PP; maintenance 2 BC)
 * Biospheres (60 PP; maintenance 1 BC)

Best choice for non-Creatives: Biospheres. The 2 extra citizens will produce 2 BC extra cash, and will appear very quickly if you use Housing colonies. That's a near-certainty, while blockade is a hypothetical risk at this stage of the game.

400 RP: Advanced Biology
Building that increases a colony's population growth by 1 "person" per 10 turns (a "person" icon represents 1M people, so the game measures growth in units of 100K) Construction project that does not produce a building but increases a colony's food output by 1 per farmer. Like most farming techs, Soil Enrichment cannot be researched by Lithovores. Ship Special Weapon, a type of biological "bomb" that, like other bombs, can only be dropped on a colony from zero range if the attacker does not have Transporters. Each Death Spores "bomb" dropped has a 10% chance of killing a colonist. Your diplomatic relations will suffer severely if you use them, but that seldom matters as Repulsive is the commonest negative pick in race design. Miniaturization: Reduces size and cost. Modifications: none.
 * Cloning Center (100 PP; maintenance 2 BC)
 * Soil Enrichment (120 PP; no maintenance)
 * Death Spores

Best choice for non-Creatives: Lithovores cannot have Soil Enrichment, and should take Cloning Center. Other races should usually take Soil Enrichment if they produce less than 4 food per farmer on their homeworld, otherwise take Cloning Center. Empires that do not take Cloning Center should make sure they use Housing colonies. Death Spores are a type of "bomb" and should not be a serious threat to yourself or your enemies while ships are slow and no-one has Transporters.

900 RP: Genetic Engineering
Achievement that gives a +5% bounus for both "Spies" (espionage and sabotage against other empires) and "Agents" (your counter-intelligence operatives). Achievement that increases population growth of all colonies by +25% and halves the effectiveness of Death Spores and Bio Terminators.
 * Telepathic Training
 * Microbiotics

Best choice for non-Creatives: depends on your race and on the other techs you have chosen or plan to choose. Races with a population growth bonus should generally choose Telepathic Training; and so should Democracies, which are weak in counter-intelligence. Races with a counter-intelligence bonus (Unification, Dictatorship) or those with a population capacity bonus (Subterranean, Tolerant, Aquatic) should generally choose Microbiotics.

1150 RP: Genetic Mutations
Construction project that upgrades a planet; Barren becomes Desert or Tundra, Desert become Arid, Tundra becomes Swamp, and Ocean, Arid, and Swamp becomes Terran. Terraforming a planet will increase not only the food production and climate, but also the planet's maximum population, although the details depnd on your race design. Construction costs depend on how often the planet has already been terraformed (possibly by another empire). For details see Growing your population and Feeding your people.
 * Terraforming

1500 RP: Macro Genetics
Fully-automated Building that increases a colony's food production by 4 without needing any farmers. Its main advantage is that its output is not reduced by blockades. Like most farming techs, Subterranean Farms cannot be researched by Lithovores. Building that increases a colony's food output by 2 per farmer. This tech can be researched by Lithovores, probably just so they don't get a free pass to the next level of Biology.
 * Subterranean Farms (150 PP; maintenance 4 BC)
 * Weather Controller (200 PP; maintenance 3 BC)

Best choice for non-Creatives: Weather Controller, as it has lower maintenance and increases food output by more. By this stage you should be able to destroy or chase away pesky little solo blockaders.

2750 RP: Evolutionary Genetics
Achievement that gives a +10% bounus for both "Spies" (espionage and sabotage against other empires) and "Agents" (your counter-intelligence operatives). Also increases morale by +10% for all governments except Unification and Galactic Unification (the game documentation gets this wrong). Achievement that increases by 1 RP the research ability of all scientist of your race; does not apply to captured colonists of other races, nor to Android Scientists.
 * Psionics
 * Heightened Intelligence

Best choice for non-Creatives: the keys are your government type and the limitations of Heightened Intelligence:
 * Governments except Unification and Galactic Unification should usually choose Psionics, as they get a +10% morale bonus which applies to all citizens of any race; this will usually increase total research by at least as much as Heightened Intelligence, and also improves farming, industrial and financial productivity. But sometimes Feudalisms / Confederations should choose Heightened Intelligence (see below).
 * Democracies need all the help they can get in counter-intelligence, so should always choose Psionics, even if they have few citizens of other races.
 * Unification and Galactic Unification governments should almost always choose Heightened Intelligence, as research is often their greatest weakness, they naturally have good counter-intelligence, and they get no morale benefits.
 * Feudalisms and Confederations are the least clear case: they urgently need a research boost whenever they can get one, but which tech will do this more effectively? In principle Psionics remains the best choice for a multi-racial empire. But Feudalism is a negative race design pick because of its poor research, and Feudalisms often go for strong population bonuses to compensate (the pre-defined Sakkra race is a good example), so even after many conquests the majority of a Feudalism's citizens may be of its founding race; in this case Heightened Intelligence boosts research more than Psionics does, and the Feudalism / Confederation should choose Heightened Intelligence.

4500 RP: Artificial Life
Ship Special Weapon, a type of biological "bomb" that, like other bombs, can only be dropped on a colony from zero range if the attacker does not have Transporters. Each Bio Terminator "bomb" dropped has a 20% chance of killing a colonist. Your diplomatic relations will suffer severely if you use them, but that seldom matters as Repulsive is the commonest negative pick in race design. Miniaturization: Reduces size and cost. Modifications: none. Achievement that increases population growth of all colonies by +50% and decreases the effectiveness of Death Spores and Bio Terminators by 75%. Not cumulative with Microbiotics.
 * Bio Terminator
 * Universal Antidote

Best choice for non-Creatives: Universal Antidote.

7500 RP: Trans Genetics
Achievement that increases all colonies' food production by +1 per farmer, even on planets that previously did not allow farming. Like most farming techs, Biomorphic Fungi cannot be researched by Lithovores. Construction project that upgrades a a Terran-class planet into a Gaia-class planet, increasing the food production and size limit. The effects vary on the depending on the inhabitants' race, see Growing your population and Feeding your people for details. Achievement that allows you to use 4 extra race design Picks however you like, except you cannot alter your current picks and you cannot choose additional penalties.
 * Biomorphic Fungi
 * Gaia Transformation (500 PP; no maintenance)
 * Evolutionary Mutation

Best choice for non-Creatives: competitive games do not usually last long enough to reach this, especially as there are higher research priorities (mostly military) including Hyper-advanced research in subjects with strong military benefits.

For aquatic or tolerant races, only Evolutionary Mutation makes sense. Usually the best pick this late in the game will be Warlord, allowing to maintain a much bigger fleet with higher experience levels.

Hyper-Advanced Biology
Biology has 1 military tech that might benefit from Hyper-Advanced miniaturization, Bio Terminator (2nd-highest tech level; Death Spores are quite low-tech and their maximum miniaturization long ago). Hyper-Advanced Biology is not generally useful.