28. Plants

Land Plants

Plant Classification | Evolution | Biology | FuseSchool

 No. Mitochondria produce carbon dioxide as a waste product of cellular respiration. 

 No. This is another term for sporangia, where spores are produced by meiosis. 

You learned about this structure when you studied photosynthesis.

What structures allow plants to readily take up carbon dioxide from the atmosphere?

Three of the following are evidence that charophytes are the closest algal relatives of plants. Select the exception.
a. similar sperm structure
b. the presence of chloroplasts
c. similarities in cell wall formation during cell division
d. genetic similarities in chloroplasts

EVOLUTION CONNECTION
DRAW IT Draw a phylogenetic tree that represents our current understanding of evolutionary relationships between a moss, a gymnosperm, a lycophyte, and a fern. Use a charophyte alga as the outgroup. (See Figure 26.5 to review phylogenetic trees.) Label each branch point of the phylogeny with at least one derived character unique to the clade descended from the common ancestor represented by the branch point.

 In plants, only the haploid stage is multicellular. 

 No. In plants, both stages are multicellular. 

 In plants, the haploid generation is always dependent on the diploid generation. 

 No. In bryophytes, the diploid generation is dependent on the haploid generation. 

 In other sexually reproducing organisms, the haploid and diploid generations are both multicellular. 

 No. The life cycle of humans, for example, includes a single-celled haploid stage and a multicellular diploid stage. 

 In other sexually reproducing organisms, the fusion of gametes forms a zygote before an embryo develops. 

 In plants, the haploid and diploid stages are both multicellular. 

This has to do with the form of the haploid and diploid stages.

Which is a key difference between alternation of generations in plants and sexual reproduction in nonplant organisms?

Introduction to Plant Diversity

 No. Although mosses lack vascular tissue, ferns do have vascular tissue. 

 No. Neither type of plant produces seeds. 

Think about how they reproduce.

Ferns and mosses are limited mostly to moist environments because __________.

Less available CO2 in the atmosphere than in the oceans

 Competition from other photosynthetic organisms such as cyanobacteria 

 No. Plants were the first photosynthesizers to colonize land. 

 No. When plants first began to inhabit terrestrial environments, there were very few herbivores of any kind. 

 All of the listed responses are correct. 

 No. Among the choices provided, only desiccation was an important challenge to be overcome as plants moved into terrestrial environments. 

What were the advantages of moving to land? What were the disadvantages?

In moving to land, which of the following challenges did plants have to overcome?

Land Plants - 4

Land Plants - 2

Which of the following characteristics of plants is absent in their closest relatives, the charophyte algae?
a. chlorophyll b
b. cellulose in cell walls
c. sexual reproduction
d. alternation of multicellular generations

The evolution of cuticle presented plants with a challenge that threatened their ability to live on land. Describe this challenge, and explain why stomata represent a solution. Compare and contrast stomata with the pores found in liverworts.

The appearance of cuticle and stomata correlated with what event in the evolution of green plants?
a. the first upright growth forms
b. the first woody tissues
c. growth on land
d. the evolution of the first water-conducting tissues

Land Plants - 3

 Plant cells have rigid cellulose walls, and algal cells do not. 

 No. Both plants and algae have cell walls made of cellulose. 

 Both plant and algal zygotes develop into embryos. 

 Algae have different types of chlorophyll molecules from plants. 

No. Both plant and algal chloroplasts contain chlorophylls a and b.

 Plants are multicellular, whereas algae are unicellular. 

 Plants have a waxy, waterproof cuticle, and algae do not. 

Think about the evidence for plants evolving from algae.

Which of the following statements about algae and plants is true?

 multicellular in algae, single-celled in most plants 

 No. Most plants possess multicellular sex organs; algae gametangia are single-celled. 

 responsible for the plant's ability to retain moisture in arid environments 

 No. The plant has numerous other adaptations that promote water conservation. 

 the site of development of the fertilized egg in algae 

 structures specialized for gradual spore discharge 

No. This describes a structure called a peristome.

 single-celled in algae, multicellular in most plants 

The form of gametangia in plants is considered to be a derived trait.

Gametangia are __________.

Evaluate the following statements regarding seeds. Select True or False for each statement.
T/F They contain an embryo.
T/F They contain nutritive tissue for the embryo.
T/F They consist entirely of diploid cells.
T/F They are also referred to as spores.

 megaspores that develop into male gametophytes and microspores that develop into female gametophytes 

 No. Heterosporous plants do produce megaspores and microspores, but megaspores develop into female gametophytes, and microspores develop into male gametophytes. 

 megaspores that bear antheridia and microspores that bear archegonia 

 No. Megaspores bear archegonia, and microspores bear antheridia. 

 spores that produce both archegonia and antheridia 

 No. Some lycophytes, which are seedless plants, are heterosporous. 

 megaspores that develop into female gametophytes and microspores that develop into male gametophytes 

Remember that "hetero-" means different.

Heterosporous plants produce __________.

Overview of Plant Classification: Vascular and Nonvascular Plants

 No. Sporophytes are found in all plants. 

 No. Apical meristems are common in all plants. 

 No. Gametophytes are found in all plants. 

 No. All plants exhibit alternation of generations. 

Review the major groups of land plants.

A major division in plant systematics is based on whether a particular species has __________.

 the vascular generation alternates with the nonvascular generation 

 No. This plant trait does not alternate between generations. 

 male plants alternate with female plants 

 No. The life cycles of all plants include a gametophyte (or haploid) generation that alternates with a sporophyte (or diploid) generation. 

 No. Only one of the other choices is correct. 

 the sporophyte generation alternates with the gametophyte generation 

What are the two generations that alternate?

Plants undergo alternation of generations in which __________.

In plants, which of the following are produced by meiosis?
a. haploid gametes
b. diploid gametes
c. haploid spores
d. diploid spores

Plants

What important role does lignin play in vascular plants?

a. It is the major component of the cuticle, which prevents plants from drying out.
b. It forms the outer layer of pollen grains.
c. It forms the tough, rigid cell walls of water-conducting cells.
d. It nourishes the embryo in seed plants.

In angiosperms, which of the following is correctly paired with its chromosome count?
(A)microspore—n
(B)zygote—n
(C)egg—2n
(D)megaspore—2n

 No. This is a type of plant tissue in the tips of roots and buds of shoots that generates new cells for lengthwise growth. 

 No. These are gamete-producing structures. 

 No. Though the stomata can close to prevent excessive desiccation, its primary function is to facilitate gas exchange. Stomata also cannot protect the plant from airborne microbes. 

 No. Peristomes are openings that allow spore release in mosses. 

Algae do not have this feature.

The development of the __________ prevents plants from drying out and protects them from microbes.

EVOLUTION CONNECTION The history of life has been punctuated by several mass extinctions. For example, the impact of a meteorite may have wiped out most of the dinosaurs and many forms of marine life at the end of the Cretaceous period (see Concept 25.4). Fossils indicate that plants were less severely affected by this mass extinction. What adaptations may have enabled plants to withstand this disaster better than animals?

 No. Tannins are compounds that are noxious and toxic to herbivores and, therefore, protect plants from excessive herbivory. 

 No. Lignin reinforces the cell walls of woody tissues. 

 No. The cuticle is the water-resistant covering of leaves. 

 No. Stomata are pores in the surfaces of leaves that allow for the exchange of gas. 

The development of this particular substance was key in allowing plants to move into terrestrial habitats.

In charophytes, __________ protect(s) zygotes from desiccation.

 No. The tracheophytes are all of the vascular land plants. 

 No. Many land plants are not vascular plants. 

 No. Seed plants include only the gymnosperms and angiosperms. 

 No. This term also applies to some bacteria. 

Think about the multicellular, dependent embryos of land plants.

Which term is most nearly synonymous with land plants?

How did plants Evolve?

What is a pollen grain?
a. male gametophyte
b. female gametophyte
c. male sporophyte
d. sperm

 Rings of cellulose-synthesizing complexes 

 No. This is true, but there is a better answer. 

 The formation of a group of microtubules between daughter nuclei during cell division 

 the structure of flagellated sperm (when present) 

Why do scientists think that land plants evolved from green algae?

Which of the following homologies is/are shared by land plants and their closest living algal relatives?

What does it mean to say that a life cycle is gametophyte dominant versus sporophyte dominant?

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