11.5.1 Plant Phylogeny: The Colonization of Land

Question 1

Plant Phylogeny: The Colonization of Land

Answer 1

• Life is thought to have originated in the sea. Plants are thought to have colonized land nearly 475 million years ago.
• To survive on land and prevent desiccation, plants developed several adaptations. Some of these adaptations include roots, vascular tissue, a waxy cuticle, the presence of stomata, seeds, and flowers.
• Plants share many characteristics with charophytes, a group of green algae, which suggest that plants arose from a charophyte ancestor.

Question 2

Plant ancestors developed several adaptations to survive on land. Some anatomical and reproductive adaptations:

Answer 2

· Roots allow a plant to access and take up water from the ground.
· Vascular tissues provide a way for the plant to conduct and transport water and nutrients to plant tissues.
· A waxy cuticle on above-ground structures prevents excessive water loss.
· Protective outer coverings prevent desiccation of spores.
· Seeds are plant embryos enclosed in a protective outer covering. The outer covering of the seed prevents desiccation of the embryo.
· Reproductive structures such as flowers allow for the protection of gametes, a location for fertilization to take place, and the retention of the zygote within the parent plant.

Question 3

Plants and charophytes (in contrast with all other types of algae) share many characteristics that suggest a common ancestry. These characteristics include:

Answer 3

· the presence of chlorophyll b and beta-carotene
· chloroplasts (shown in illustration to the left)
that are similar in structure
· biochemical similarities in cell wall and
peroxisome composition
· similar mitotic processes
· sperm structure that is similar
· similar DNA sequences (DNA homology)

Question 4

Which of the following is not an adaptation plant ancestors developed in order to survive dessication?

Answer 4

• chloroplasts

Question 5

Which of the following does not serve as a major terrestrial adaptation for plants?

Answer 5

• cellulose

Question 6

Plants are thought to have colonized land approximately ______ years ago

Answer 6

• 475 million

Question 7

True or false?

Modern day charophytes are ancestors of plants.

Answer 7

• false

Question 8

Which of the following statements is not evidence for the origin of plants from charophytes?

Answer 8

• In both groups, the zygote that forms after fertilization is enclosed in a protective coat

Question 9

Which of the following characteristics is present in plants, but absent in charophytes, plant’s closest relative?

Answer 9

• seeds