Biology Ecology and Evolution Flashcards

What is the primary source of energy for most ecosystems on Earth?

Answer: Solar energy captured by photosynthesis

Photosynthetic organisms (plants, algae, cyanobacteria) convert solar energy into chemical energy, forming the energetic foundation of most food webs.

Which type of speciation occurs when a physical barrier geographically separates a population?

Answer: Allopatric speciation

Allopatric speciation occurs when a population is divided by a geographic barrier, preventing gene flow and allowing the groups to diverge into separate species.

In a food web, what is the effect of removing a keystone predator?

Answer: The prey population explodes, destabilizing the ecosystem

Without the keystone predator, prey populations grow unchecked (trophic cascade), often overgrazing or outcompeting other species and reducing biodiversity.

Which biogeochemical cycle involves bacteria converting atmospheric nitrogen into forms usable by plants?

Answer: Nitrogen cycle

In the nitrogen cycle, nitrogen-fixing bacteria convert atmospheric N₂ into ammonia (NH₃), which plants can absorb and use to build proteins.

What does 'r-selected' reproductive strategy describe in ecology?

Answer: Species that produce many offspring with little parental investment

r-selected species maximize reproductive rate by producing many offspring with minimal parental care, thriving in unstable or unpredictable environments.

What evolutionary evidence is provided by the existence of vestigial structures?

Answer: Species share common ancestry with ancestors that used those structures

Vestigial structures are reduced, functionless remnants of structures that were functional in ancestors, indicating shared evolutionary history.

Which process transfers energy and matter from dead organisms back to the ecosystem?

Answer: Decomposition

Decomposers (fungi and bacteria) break down dead organic matter, recycling nutrients back into the soil and atmosphere for use by producers.