Herpetology cheat sheet

Two major groups

Herpetology studies amphibians and reptiles. These are different evolutionary groups, rather than one biological class.

Frogs and salamanders are amphibians; snakes and turtles are reptiles.

Skin and water

Amphibian skin is generally permeable. Reptiles generally have keratinised scales that reduce water loss.

Compare a frog’s moist skin with a lizard’s scaly skin.

Life cycles

Many amphibians change from an aquatic larval stage to a different adult form. Important exceptions occur.

A tadpole developing into a frog is metamorphosis.

Ectothermy

Most living amphibians and reptiles rely strongly on environmental heat. Behaviour helps them regulate body temperature.

Basking increases heat gain; moving into shade reduces it.

Amniotic development

Reptiles belong to the amniotes: embryonic membranes support development away from open water. Reptile reproduction is diverse; some species give birth to live young.

An amnion is an embryonic membrane, not a synonym for a hard eggshell.

Gas exchange

Many amphibians exchange gases across moist skin as well as through lungs or gills. The balance changes with species and life stage; reptiles breathe primarily using lungs.

A permeable respiratory surface also creates a route for water loss and contaminant exposure.

Adaptation and selection

An adaptation is a heritable feature shaped by selection across generations. An individual moving into shade changes its behaviour; it does not evolve during that afternoon.

Separate short-term thermoregulation from evolutionary change in a population.

Field sampling

Use the same search area, effort and conditions when comparing observations. Detectability varies with temperature, season and activity, so a low count need not mean absence.

Record animal observations per survey-hour, together with weather and habitat.

Worked example: occupancy

A team detects frogs at 6 of 10 surveyed ponds. The observed detection proportion is 6 ÷ 10 = 0.60. Without repeat visits, this does not estimate true occupancy without assumptions about detection.

Report “detected at 60% of surveyed ponds”, rather than “only 60% of ponds contain frogs”.

Common mistake: a single life cycle

Avoid treating the familiar frog diagram as universal. Amphibians include direct-developing and permanently aquatic forms, and reptile eggs and parental care also vary.

Qualify broad statements with “many”, “most” or a named species where needed.

Check your understanding

Does a lizard basking in sunlight demonstrate evolution?

No. It demonstrates behavioural thermoregulation; evolution concerns inherited population change across generations.

Curriculum connections

Sources