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 head 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 (corn; 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 fertilization.

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

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 fruit (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 fertilization (in a simplified way).

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

Explain what germination is and which three external conditions a seed needs (water, oxygen, and a suitable temperature), and discuss 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 parent plant reduces competition.

Dormancy synchronizes germination with the favorable 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 (open soil, light, nutrient-rich ashes).

A coastal conservation team attempts to eradicate two invasive species in a dune system:

• Case 1: The sour fig (Carpobrotus edulis), a creeping succulent plant, is mechanically crushed and shredded using heavy machinery 'in situ'. Four months later, the plant's cover density has tripled throughout the treated area.

• Case 2: Pampas grass (Cortaderia selloana), a giant dioecious tussock grass, is cut down to ground level just at the end of summer, removing the adult specimens. The following spring, tens of thousands of seedlings sprout within a radius of more than 2 km downwind.

1. a) Justify the failure of both interventions, explaining which reproductive strategy (sexual or asexual) and which type of propagule or diaspore each species exploited to react with such vigor.
2. b) Design a methodological modification for the eradication of sour fig that prevents the dispersal of vegetative propagules and ensures the definitive elimination of the biomass bank without eroding the dune.
3. c) Propose three strictly reproductive biological criteria (relating to pollination type, fecundity rate, dispersal, or seed persistence) that justify legally prohibiting the sale of an ornamental plant in gardening before it demonstrates its invasive potential.