GPP - respiration = NPP

“Only ~10% of energy climbs each step of a food chain — which is why lions are rare and grass everywhere.”

Net primary productivity. Use it when producers.

GPP - respiration = NPP

food chain vs food web

“Only ~10% of energy climbs each step of a food chain — which is why lions are rare and grass everywhere.”

A food chain is a single linear path of who eats whom; a food web is the interconnected network of many overlapping food chains.

primary succession vs secondary succession

“Only ~10% of energy climbs each step of a food chain — which is why lions are rare and grass everywhere.”

Primary succession begins on lifeless bare surfaces (new rock) and is slow; secondary succession restarts on soil that already exists (after a fire) and is faster.

in-situ conservation vs ex-situ conservation

“Only ~10% of energy climbs each step of a food chain — which is why lions are rare and grass everywhere.”

In-situ protects species in their natural habitat (national parks); ex-situ protects them outside it (zoos, seed banks).

Watch out: Energy is recycled through an ecosystem like nutrients

“Only ~10% of energy climbs each step of a food chain — which is why lions are rare and grass everywhere.”

Energy flows one way and is lost as heat at each level; only nutrients are recycled.

Natural selection

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Individuals better suited to their environment survive and reproduce more, shifting the population over generations.

Memory trick: populations evolve, not individuals.

Natural selection — common mistake

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

A frequent error is thinking individuals evolve within their lifetime. In reality, individuals better suited to their environment survive and reproduce more, shifting the population over generations.

Memory trick: populations evolve, not individuals.

Evidence for evolution

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Fossils, homologous organs and molecular similarities all support common descent.

Memory trick: homologous = common ancestry; analogous = similar function.

Evidence for evolution — common mistake

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

A frequent error is confusing homologous with analogous organs. In reality, fossils, homologous organs and molecular similarities all support common descent.

Memory trick: homologous = common ancestry; analogous = similar function.

Hardy-Weinberg principle

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Allele frequencies stay constant unless disturbed by selection, mutation, drift, migration or non-random mating.

Memory trick: deviation from Hardy-Weinberg signals evolution.

Hardy-Weinberg principle — common mistake

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

A frequent error is thinking evolution needs no cause to happen. In reality, allele frequencies stay constant unless disturbed by selection, mutation, drift, migration or non-random mating.

Memory trick: deviation from Hardy-Weinberg signals evolution.

Genetic drift

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Chance changes allele frequencies strongly in small populations.

Memory trick: drift dominates in small populations.

Genetic drift — common mistake

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

A frequent error is thinking drift matters most in large populations. In reality, chance changes allele frequencies strongly in small populations.

Memory trick: drift dominates in small populations.

Speciation

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Reproductive isolation splits one species into two that can no longer interbreed.

Memory trick: a species is defined by reproductive isolation.

Speciation — common mistake

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

A frequent error is thinking geographic distance alone defines a species. In reality, reproductive isolation splits one species into two that can no longer interbreed.

Memory trick: a species is defined by reproductive isolation.

Types of selection

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Selection can be stabilising, directional or disruptive, reshaping trait distributions differently.

Memory trick: stabilising favours the average; disruptive the extremes.

Types of selection — common mistake

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

A frequent error is assuming selection always shifts the mean one way. In reality, selection can be stabilising, directional or disruptive, reshaping trait distributions differently.

Memory trick: stabilising favours the average; disruptive the extremes.

Adaptive radiation

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

One ancestor diversifies into many forms filling different niches, as in Darwin's finches.

Memory trick: one ancestor -> many niche specialists.

Adaptive radiation — common mistake

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

A frequent error is thinking radiation is slow single-line change. In reality, one ancestor diversifies into many forms filling different niches, as in Darwin's finches.

Memory trick: one ancestor -> many niche specialists.

Hardy-Weinberg: p^2 + 2pq + q^2 = 1

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Genotype frequencies at equilibrium. Use it when no evolutionary forces acting.

Hardy-Weinberg: p^2 + 2pq + q^2 = 1

p + q = 1

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Allele frequencies sum to one. Use it when two-allele gene.

p + q = 1

Homologous organs -> divergent evolution

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Structural evidence. Use it when common ancestor, different functions.

Homologous organs -> divergent evolution

homologous organs vs analogous organs

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Homologous organs share a common ancestral structure but differ in function (divergent evolution); analogous organs share function but not ancestry (convergent evolution).

natural selection vs genetic drift

“Whales still carry tiny hip bones — fossils of the legs of their land-walking ancestors.”

Natural selection changes allele frequencies non-randomly by fitness; genetic drift changes them randomly, especially in small populations.