Angiosperm Reproduction and Biotechnology

Distinguish between pollination and fertilization.

If flowers had shorter styles, pollen tubes would more easily reach the embryo sac. Suggest an explanation for why very long styles have evolved in most flowering plants.

Does the life cycle of humans have any structures analogous to plant gametophytes? Explain your answer. (See Figures 13.5 and 13.6.)

A correlation is a way to describe the relationship between two variables. In a positive correlation, as the values of one of the variables increase, the values of the second variable also increase. In a negative correlation, as the values of one of the variables increase, the values of the second variable decrease. Or there may be no correlation between the two variables. If researchers know how two variables are correlated, they can make a prediction about one variable based on what they know about the other variable. (a) Which variable(s) is/are positively correlated with the volume of nectar production in this genus? (b) Which is/are negatively correlated? (c) Which show(s) no clear relationship?

(a) Which Mimulus species would you categorize as mainly asexual reproducers? Why? (b) Which species would you categorize as mainly sexual reproducers? Why?

(a) Which species would probably fare better in response to a pathogen that infects all Mimulus species? (b) Which species would fare better if a pathogen caused hummingbird populations to dwindle?

What are three ways that flowering plants avoid self-fertilization?

The seedless banana, the world's most popular fruit, is losing the battle against two fungal epidemics. Why do such epidemics generally pose a greater risk to asexually propagated crops?

Self-fertilization, or selfing, seems to have obvious disadvantages as a reproductive “strategy” in nature, and it has even been called an “evolutionary dead end.” So it is surprising that about 20% of angiosperm species primarily rely on selfing. Suggest a reason why selfing might be advantageous and yet still be an evolutionary dead end.

Compare traditional plant-breeding methods with genetic engineering.

Why does Bt maize have less fumonisin than non-GM maize

In a few species, chloroplast genes are inherited only from sperm. How might this influence efforts to prevent transgene escape?

“Bt maize” 

(A) is resistant to various herbicides, making it practical to weed rice fields with those herbicides. 

(B) contains transgenes that increase vitamin A content. 

(C) includes bacterial genes that produce a toxin that reduces damage from insect pests. 

(D) is a “boron (B)-tolerant” transgenic variety of maize.

A fruit is 

(A) a mature ovary. 

(B) a mature ovule. 

(C) a seed plus its integuments. 

(D) an enlarged embryo sac.

Double fertilization means that 

(A) flowers must be pollinated twice to yield fruits and seeds. 

(B) every egg must receive two sperm to produce an embryo. 

(C) one sperm is needed to fertilize the egg, and a second sperm is needed to fertilize the polar nuclei. 

(D) every sperm has two nuclei

Which statement concerning grafting is correct? 

(A)    Stocks and scions refer to twigs of different species. 

(B)    Stocks and scions must come from unrelated species. 

(C)    Stocks provide root systems for grafting.

(D)    Grafting creates new species.

Some dioecious species have the XY genotype for male and XX for female. After double fertilization, what would be the genotypes of the embryos and endosperm nuclei? 

(A)    embryo XY/endosperm XXX or embryo XX/endosperm XXY 

(B)    embryo XX/endosperm XX or embryo XY/endosperm XY 

(C)    embryo XX/endosperm XXX or embryo XY/endosperm XYY 

(D)    embryo XX/endosperm XXX or embryo XY/endosperm XXY

A small flower with green petals is most likely

(A) bee-pollinated.

(B) bird-pollinated.

(C) bat-pollinated.

(D) wind-pollinated.

The black dots that cover strawberries are actually fruits formed from the separate carpels of a single flower. The fleshy and tasty portion of a strawberry derives from the receptacle of a flower with many separate carpels. Therefore, a strawberry is

(A) a simple fruit with many seeds.

(B) both multiple fruits and accessory fruit.

(C) both a simple fruit and an aggregate fruit.

(D) both an aggregate fruit and an accessory fruit.

Draw and label the parts of a flower. 

In a short essay (100–150 words), discuss how a flower's ability to reproduce with other flowers of the same species is an emergent property arising from floral parts and their organization.

This colorized SEM shows pollen grains from six plant species. Explain how a pollen grain forms, how it functions, and how pollen grains contributed to the dominance of angiosperms and other seed plants.

With respect to sexual reproduction, some plant species are fully self-fertile, others are fully self-incompatible, and some exhibit a “mixed strategy” with partial self-incompatibility. These reproductive strategies differ in their implications for evolutionary potential. How, for example, might a self-incompatible species fare as a small founder population or remnant population in a severe population bottleneck (see Concept 23.3), as compared with a self-fertile species?

Critics of GM foods have argued that transgenes may disturb cellular functioning, causing unexpected and potentially harmful substances to appear inside cells. Toxic intermediary substances that normally occur in very small amounts may arise in larger amounts, or new substances may appear. The disruption may also lead to the loss of substances that help maintain normal metabolism. If you were your nation’s chief scientific advisor, how would you respond to these criticisms?

Humans have engaged in genetic manipulation for millennia, producing plant and animal varieties through selective breeding and hybridization that significantly modify genomes of organisms. Why do you think modern genetic engineering, which often entails introducing or modifying only one or a few genes, has met with so much opposition? Should some forms of genetic engineering be of greater concern than others? Explain.