Plant reproduction

Name the four whorls of a complete flower (calyx, corolla, androecium, and gynoecium) and state the parts and function of each one.

Distinguish between a flower and an inflorescence, and give an example of an inflorescence (the capitulum of the sunflower, the spike of wheat, the umbel of the carrot), explaining what advantage grouping many small flowers can have.

Explain what hermaphrodite flowers and unisexual flowers are, and what monoecious and dioecious plants are, with an example of each case (maize; kiwi or holly).

Look at the sectioned flower in the image. a) Indicate which numbers correspond to the androecium and gynoecium, and which parts form each one. b) Explain the function of structures 4 and 5 during reproduction. c) Describe what happens to structure 6 and the ovules it contains after fertilisation.

Differentiate between pollination and fertilisation, indicating what travels in each process, through where, and which floral structures are involved.

Many plants with hermaphrodite flowers cannot self-fertilise. Explain two mechanisms that prevent it (staggered maturation of stamens and stigma, genetic self-incompatibility) and discuss what evolutionary advantage preventing self-fertilisation has even though it risks ending up without seeds.

The orchid Ophrys mimics a female bee and attracts males, which pollinate while attempting to copulate. Explain what coevolution between flower and pollinator is, which traits of the flower (shape, colour, smell) take part in the deception, and why such extreme specialisation is at once an advantage and a risk.

What is nectar and which floral structures produce it (nectaries)? Explain the "contract" it establishes between the plant and the pollinator (food in exchange for pollen transport).

Compare the floral adaptations of anemophilous plants (wind-pollinated, such as grasses) and entomophilous plants (insect-pollinated): flowers, pollen, nectar, and efficiency of the process.

Which floral structure does the fruit develop from, and which does the seed develop from? Give an example of a fleshy fruit and a dry fruit, indicating which part we eat in each case.

Name the parts of the pericarp of a fleshy fruit (exocarp, mesocarp and endocarp) using the cherry as an example, and explain the difference between a true fruit and a false one (a pseudofruit: the apple, the strawberry).

Describe the reproductive cycle of an angiosperm from when a pollen grain reaches the stigma until the seed is formed: pollen germination, pollen tube, and double fertilisation (in a simplified way).

Explain what germination is and which three external conditions a seed needs (water, oxygen and a suitable temperature), discussing why seeds kept in a dry jar do not germinate.

Relate the structure of each diaspore to its disperser: the pappus of the dandelion and the wings of the maple fruit with the wind, and the coconut with water. Explain which traits (lightness, surface, buoyancy) each medium selects and why dispersing far from the mother reduces competition.

Dormancy synchronises germination with the favourable season. Explain three mechanisms that maintain it (a hard impermeable coat, chemical inhibitors, the need for a cold period — stratification) and which signal breaks each one, giving an example of a plant for each mechanism.

Some Mediterranean pines keep their cones closed until a fire passes (serotiny) and certain seeds only germinate with smoke. Explain what these adaptations to fire consist of and what advantage germinating just after a fire has (free soil, light, nutrient-rich ashes).