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Biology 11 Enriched: The Evolution of Seed Plants (30)

Unit Topics

1. Analyze how the increasing complexity of gymnosperms and angiosperms contribute to survival in a land environment

a) Examine gymnosperms and describe the characteristics that unify themb) Explain how gymnosperms are adapted for survival in a land environment with respect to the following: alternation of generations, roots, stems, leaves, seeds, pollen, vascular tissue (p.348 to 349)c) Examine angiosperms and describe characteristics that unify them (p.350 to 351)d) Use specimens to differentiate between monocots and dicots (p.623 )e) Describe how angiosperms are adapted for survival in a land environment, with respect to alternation of generations, flowers, pollen, enclosed seeds, fruit, roots, stems, leaves, vascular tissuef) Compare the ways in which mosses, ferns, gymnosperms, and angiosperms have adapted to a land environment (p.342 +)

Vocabulary

adaptation, alternation of generations, colonial, dicots, enclosed seeds, flowers, fruit, leaves, monocots, multicellular, pollen, roots, seeds, stems, unicellular, vascular tissue

Overview: Transforming the Worlda) The seed arose about 360 million years ago.i) A seed consists of an embryo and its food supply, surrounded by a protective coat. ii) When mature, seeds are dispersed from their parent.iii) Because it nourishes and protects the embryo yet can separate from the mother plant, a seed is analogous to a detachable, mobile uterus.b) Seeds are the key adaptation that enabled seed plants to be the dominant producers on land, making up the great majority of plant biodiversity.c) Agriculture, the cultivation and harvest of plants (especially angiosperms), began 12,000 years ago.i) Humans began to cultivate plants independently in various regions, including the Near East, East Asia, Africa, and the Americas.d) The cultivation of plants was the single most important cultural change in the history of humanity; it made possible the transition from hunter-gatherer societies to permanent settlements.

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Describe the characteristics that distinguish seed plants from other vascular plants:

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What are some advantages of a reduced

(microscopic) gametophyte in the seed

plants?

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The Evolution of the Seed

-Seed plants exhibit heterospory (Male and Female spores).

-The female spore is called a megaspore and is produced by megasporangium inside the

parent sporophyte.

-The megasporangium with its surrounding integument (protective layer) is called an

ovule. Following fertilization, the ovule develops into the seed containing the spropohyte

embryo and food supply.

-The seed is covered by a protective seed cote derived from the integument.

-The male spore is called a microspore and is produced inside the microsporangium or

pollen sac.

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Gymnosperms

-Gymnosperms are plants that have vascular tissue and seeds! However, their seeds are

called “naked” as they are not protected within ovaries.

-Some gymnosperms that you may recognize are:

-All gymnosperms possess cones, which are modified leaves of the sporophyte called

sporophylls. Each “leaf” or scale contains a sporangium that produces spores by meiosis.

Unlike seedless plants, these spores are not released but develop into the gametophyte

within the cone. The gametophyte later releases gametes that combine to form a new

sporophyte.

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Fir Yew Cedar

Ginko bilboa Cycad

-Examine the Gymnosperm Life Cycle below:

1. Where are the male and female gametophytes in seed plants?

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2. What is a seed?

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3. In the gymnosperm life cycle, what does the pollen

grain represent?

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4. How does pollen help gymnosperms to adapt to life on land?

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4. How do seeds help gymnosperms to adapt to life on land?

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5. As land plants evolved to become better adapted to life on land, what happened to the

relative dominance of the sporophyte and gametophyte generations? (use the diagram

below to answer this question.)

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Overview of Alternation of Generations in Plants

Angiosperms

-Angiosperms are flowering plants that have vascular tissue and enclose their seeds inside

of fruit. They are the largest and most successful group of plants and include:

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-Analyse the diagram right to understand how the

part of the flower perform the same functions as

the cones in gymnosperms.

-Label the diagram of the flower below and answer

the questions that follow (text 350)

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1. What are the functions of a flower?

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2. How did fruit containing enclosed seeds

evolve?

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3. Which part of a flower develops into the seed? ________________________________

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4. Which part of the flower develops into the fruit? ______________________________

5. How does pollination take place?

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-Examine the Angiosperm Life Cycle animation on the text website (Chapter 17) and use

text 351 to illustrate the angiosperm life cycle diagram below

Fruit Formation

What part of the flower develops into a fruit? __________________________________

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This table compares different types of fruits:

Many fruits are

adapted to assist

in seed

dispersal:

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This diagram shows the phylogenetic relationships between the various plant groups

Label: flowers, seeds, vascular tissue and embryos.

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