5 Steps to a 5 AP Biology, 2014-2015 Edition

158 ❯ STEP 4. Review the Knowledge You Need to Score High

lichenconglomerate. Most have both asexual andsexual reproductive stages. These

organisms are considered to be the ancestors of plants.

5. Brown algae.Known as phaeophyta,most of these protists are multicellularand live in
   marineenvironments. Two members to know are kelpandseaweed.


6. Red algae.Known as rhodophyta, they get their color from a pigment called phycobilin.
   Most of these multicellularprotists live in the ocean and produce gametes that do not have
   flagella. Many live in deep waters and absorb nonvisible light via accessory pigments.

Kingdom Plantae

Classification of plants is very similar to classification of the animal kingdom, except that

plants are divided into divisions instead of phyla. So, instead of “Karaoke players can order

free grape soda,” remember “Karaoke dancerscan order free grape soda.”

Reality again, folks... you do not need to become experts in the evolutionary history

of plants, but you should be able to understand a phylogenetic representation of how the

various plant types evolved.

Chlorophytes→bryophytes→seedless vascular plants→gymnosperms→angiosperms

Chlorophytesare green algae. Scientists have found enough evidence to conclude that they

are the common ancestors of land plants. Plants are said to have experienced four major

evolutionary periods since the dawn of time, described in the following sections.

Bryophytes

Bryophyteswere the first land plants to evolve from the chlorophytes. They include

mosses, liverworts, and hornworts. Prior to bryophytes, there was no reason for these organ-

isms to worry about water loss because they lived in water and had unlimited access to the

treasured resource. But in order to survive on land, where water was no longer unlimited,

two evolutionary adaptations in particular helped them survive:

1. A waxy cuticlecover to protect against water loss.


2. The packaging of gametes in structures known as gametangia.
   Bryophyte sperm is produced by the male gametangia, the antheridia.Bryophyte eggs are
   produced by the female gametangia, the archegonium.The gametangia provide a safe
   haven because the fertilization and development of the zygote occur within the protected
   structure.
   Because they lack xylem and phloem, bryophytes are also known as nonvascular plants.
   This lack of vascular tissue combined with the existence of flagellated sperm results in a
   dependence on water. For this reason, bryophytes must live in damp areas so they do not dry
   out. There are three nonvascular plants you should know about: mosses, liverworts, and horn-
   worts. Mosses are special in that, unlike all other plants, the dominant generation in their life
   cycle is the haploid gametophyte. The moss sporophyte is tiny, short lived, and reliant on the
   gametophyte for nutritional support. One interesting fact about liverworts is that in addition
   to the alternation of generations life cycle, they are able to reproduce asexually.

Seedless Vascular Plants

The transition for plants from water to land was a tricky one. They needed to find a way

to use the nutritional resources of the minerals and water found in soil, while not denying

themselves access to the light needed for photosynthesis. Another problem facing these

KEY IDEA

KEY IDEA

CT teacher:
“Know plant
evolution very
well. There are
a lot of potential
questions here.
Including essays.”

KEY IDEA