Seed Plants

What are the five key derived traits shared by all seed plants?

Reduced gametophytes, heterospory, ovules, pollen, and seeds.

In seed plants, what is the ecological and evolutionary relationship between the gametophyte and the sporophyte?

The gametophytes are microscopic and dependent on the dominant sporophyte for protection and nutrition.

What is heterospory in seed plants?

The production of two distinct types of spores: microspores (which form male gametophytes) and megaspores (which form female gametophytes).

What specific spore structure gives rise to a male gametophyte in seed plants?

Microspore

What specific spore structure gives rise to a female gametophyte in seed plants?

Megaspore

What structural components constitute a gymnosperm ovule?

A megasporangium (2n), a megaspore (n), and a protective integument (2n).

What is the function of the integument in a seed plant ovule?

It is a layer of sporophyte tissue (2n) that surrounds and protects the megasporangium.

How did the evolution of pollen eliminate the need for liquid water during fertilization?

Pollen grains house the male gametophyte and travel via wind or animals, growing a pollen tube directly to the ovule to deliver sperm

What are the three main components of a mature seed?

An embryo (2n), a food supply, and a protective seed coat (2n).

Why do seeds provide a survival advantage over unprotected spores?

Seeds carry their own nutrient reserves, can remain dormant for long periods, and are structurally equipped for long-distance dispersal.

Which plant generation is dominant in nonvascular plants such as Hepatophyta and Bryophyta?

Gametophyte

Which feature distinguishes liverworts (Hepatophyta) from mosses (Bryophyta) regarding asexual reproduction?

Hepatophyta possess gemmae cups for asexual reproduction, whereas Bryophyta lack gemmae cups.

Why do nonvascular plants require liquid water for sexual reproduction?

They produce flagellated sperm that must swim through a film of water to reach the egg.

Which vascular leaf type contains a single unbranched vein and is characteristic of Lycophyta?

Microphylls

Which vascular leaf type has a highly branched vascular network and is found in Monilophyta, gymnosperms, and angiosperms?

Megaphylls

Approximately when do the earliest gymnosperm fossils appear in the geological record?

Approximately 305 million years ago (MYA).

Which anatomical adaptations allowed gymnosperms to thrive as Earth's climate became drier?

Thick cuticles and thin, needle-like or scale-like leaves.

Which gymnosperm phylum features palm-like leaves, motile sperm, and separate ovulate and staminate plants?

Cycadophyta

Which gymnosperm phylum is characterized by fan-shaped deciduous leaves and motile sperm?

Ginkgophyta

Which two gymnosperm phyla retain ancestral motile sperm?

Cycadophyta and Ginkgophyta

Which two gymnosperm phyla possess non-motile sperm?

Gnetophyta and Coniferophyta

What type of plant is defined as dioecious?

A plant species where male (staminate) and female (ovulate) reproductive structures are located on separate individual plants.

Which gymnosperm phylum typically bears both ovulate and staminate cones on the same individual plant?

Coniferophyta

In conifer pollen cones, which cells undergo meiosis to produce haploid microspores?

Microsporocytes (2n)

In a gymnosperm ovule, which cell undergoes meiosis to produce megaspores?

Megasporocyte (2n)

How many megaspores survive after meiosis in a gymnosperm megasporangium?

One surviving megaspore (n)

By which cell division process does a surviving gymnosperm megaspore develop into a female gametophyte?

Mitosis

What is the ploidy level of the food reserves in a mature gymnosperm seed?

Haploid (n), because the food reserve is formed from female gametophyte tissue.

What is the ploidy level of the seed coat in gymnosperms?

Diploid (2n), derived from parental sporophyte tissue (integument).

Approximately when do the earliest angiosperm fossils appear?

Approximately 145 million years ago (MYA).

What is the age and identity of the fossil flower plant Archaefructus sinensis?

It is an early angiosperm fossil dating back approximately 125 million years.

What structural role do stamens play in a flower?

Stamens are microsporophylls that produce microspores, which develop into pollen grains containing male gametophytes.

What are the two sub-components of a stamen?

Anther and filament

What structural role do carpels play in a flower?

Carpels are megasporophylls that produce megaspores, which form female gametophytes (embryo sacs).

What three distinct anatomical regions compose a carpel?

Stigma, style, and ovary

What is a fruit in botanical terms?

A mature ovary (often with accessory tissues) that functions to protect seeds and facilitate their dispersal.

What is the female gametophyte of an angiosperm called?

Embryo sac

In angiosperms, what mitotic division occurs inside the growing pollen grain to produce sperm cells?

The generative cell divides mitotically to produce two haploid sperm cells.

What role does the tube cell play during angiosperm pollination?

The tube cell produces the pollen tube that grows down through the style into the ovule.

What two distinct fertilization events occur during angiosperm double fertilization?

1. One sperm fertilizes the egg cell to form the diploid (2n) zygote.

2. The second sperm fuses with the two polar nuclei to form the triploid (3n) endosperm.

What is the ploidy level and function of endosperm in angiosperm seeds?

It is triploid (3n) and serves as a nutrient supply for the developing embryo.

What is a cotyledon?

A seed leaf present within the plant embryo.

How many cotyledons do monocot embryos possess versus dicot embryos?

Monocot embryos have one cotyledon, whereas dicot embryos have two cotyledons.

Which angiosperm group is characterized by the leaf venation pattern shown on the left?

Monocots (parallel leaf veins)

What type of leaf venation pattern is characteristic of dicots?

Netlike leaf venation

Which arrangement of stem vascular bundles corresponds to monocots versus dicots?

Monocots have scattered vascular bundles (left); dicots have primary vascular bundles arranged in a ring (right).

Which root system architecture is typically present in dicots?

A taproot system (main root usually present), as shown on the right.

What root system structure typically characterizes monocots?

A fibrous root system with no main taproot.

How do pollen grains differ between monocots and dicots regarding opening count?

Monocot pollen grains have one opening; dicot pollen grains have three openings.

In what numerical multiples are floral organs usually arranged in monocots?

Multiples of three

In what numerical multiples are floral organs usually arranged in dicots?

Multiples of four or five

Which major group of insect pollinators experienced significant adaptive radiation alongside angiosperms during the Cretaceous period?

Hymenoptera, Diptera, and Lepidoptera

What is the global purpose of facilities such as the Svalbard Global Seed Vault?

To preserve crop seed diversity against global disasters, climate change, and loss of genetic variation.