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Plant life


Characteristics of plants

* Eukaryotes – have an organized cell structure. Nuclei, and other cell organelles.

animal and fungus cells are also eukaryotic.

* Prokaryotes – much less organized. (only in bacteria and archaea)

Levin 8e/Wiley fig 8-37 w174

* Plant cells have a cell membrane (a lipid bilayer ) and a cell wall (cellulose)

Animal cells only have a cell membrane.

* Plant cells have one huge vacuole (organelle for storage)

Animal cells a few tiny vacuoles (they aren’t even visible in this diagram)

* Plant cells have an organelle called a chloroplast.

Using energy from light, this is where photosynthesis occurs.


* Most plants don’t need to eat food (they producer their own food)

* Organisms that make their own food are called Autotrophs or Producers

** Weirdness alert – a few plants are heterotrophs – they do need to get food from other sources. So a few plants are parasites on other plants, or consume nutrients from dead organisms.

This is Cactus Mistletoe (Tristerix aphylla), from Chile.  This is a bright red parasitic plant. It can only live on a cactus.

{ Scott Zona, http://www.flickr.com/photos/scottzona/5187034058/ }

Echinopsis chiloensis and Tristerix aphylla


What plants need

CO2 (carbon dioxide gas)
H2O (water)
Trace amount of minerals, absorbed through the plant’s roots.

What plants produce

Sugars (an organic molecules) + O2 (oxygen gas)

Chemistry Photosynthesis

Types of plants and how they evolved

{ http://greatneck.k12.ny.us/gnps/shs/dept/science/krauz/bio_h/handouts_000.html }

Plant cladogram larger

Seedless plants

Green alage

Is algae even a plant? Red algae and brown algae aren’t plants – they’re protists – they are classified in an entirely different kingdom of life. And don’t get me started on “Blue-green algae” – they aren’t plants or Protists – they’re really a type of photosynthetic bacteria. But what about green algae – are they plants? It depends on whom you ask:

{ http://www.slideshare.net/VijayaraghavanGonuguntla/effluent-treat }

Green Algae_Pond

The Green Algae Tree of Life (GrAToL)

The Green Algae Tree of Life (GrAToL)

Botanists (plant scientists) consider green algae plants. They perform photosynthesis using chlorophyll.  They are the ancestors of modern day land-plants. They’re part of the land-plant family tree. End of story -> Plants! 🙂

But Zoologists (animal and protist scientists) classify green algae as protozoans (not plants) In this view, green algae can’t be plants because:

1) Most are single-celled (unicellular), too small to be seen without a microscope.
2) When not single celled, they live in colonies. Don’t form plant tissue.
3) They can move on their own. Some swim with flagella.
4)  They have no vascular system to transport nutrients.
5) They do not have true roots, shoots, or veins.
6)  They have no stems, leaves or roots.

Why can’t the answer be a simple “yes they are” or “no they are not?” Because life wasn’t created with well-defined boundaries – and life today still doesn’t have such boundaries. Life started as simple organisms, and developed over time, slowly branching out to create new forms, with new characteristics. Today’s green algae resembles the early forms of life that later gave rise to both plants and to protists.  It is a kind of “living fossil.

Plant and green algae family tree

{Figure 1. Phylogenetic relationships among the main lineages of green plants. The tree topology is a composite on accepted relationships based on molecular phylogenetic evidence (Lewis & McCourt, 2004; McCourt et al., 2004; Lemieux et al., 2007; Rodríguez-Ezpeleta et al., 2007; Turmel et al., 2007b; Becker & Marin, 2009; Turmel et al., 2009; Cocquyt et al., 2010; Finet et al., 2010; Marin & Melkonian, 2010; Zechman et al., 2010). Uncertain phylogenetic relationships are indicated by polytomies. The divergence times are rough approximations based on the fossil record and molecular clock estimates (Colbath, 1983; Knoll, 1992; Yoon et al., 2004; O’Kelly, 2007; Herron et al., 2009). These age estimates should be interpreted with care as different molecular clock studies have shown variation in divergence times between major green plant lineages. Drawings illustrate representatives of each lineage: (1) Acetabularia, (2) Pediastrum, (3) Chlorella, (4) Tetraselmis, (5) Picocystis, (6) Ostreococcus, (7) Micromonas, (8) Crustomastix, (9) Monomastix, (10) Pyramimonas, (11) Pycnococcus, (12) Pseudoscourfieldia, (13) Nephroselmis, (14) Prasinococcus, (15) Verdigellas (a: general habit, b: individual cells in a gelatinous matrix), (16) Mesostigma, (17) Chlorokybus, (18) Klebsormidium, (19) Chara, (20) Xanthidium, (21) Coleochaete, (22) Chaetosphaeridium, (23) Ranunculus.}


{ http://www.hiddenforest.co.nz/bryophytes/what.htm }

Bryophytes are a group of small, simple, green, land dwelling plants (a few are aquatic)
Includes: Hornworts, Liverworts, and Mosses.

{ http://antranik.org/the-evolution-of-plants/ }

Moss: small, flowerless plant. Grows in dense green clumps, in damp, shady locations. Have simple, one-cell thick leaves, covering a thin stem. No seeds or any vascular tissue.

The largest group of land plants – 25,000 different species
Found in areas which are humid and damp, with a cold to moderately warm climate.
Have no internal means for transporting water or nutrients.
Their “leaves” are not equivalent to the leaves of vascular plants. Mostly one cell thick.
Don’t have any roots.
Do not produce flowers, never produce seeds.

Vascular plants

Flash animation showing water & nutrient transport through vascular plants

Animation on flow through xylem and phloem

Biology, Eighth Edition (Raven) Chapter 38: Transport in Plants



Text below adapted from “Vascular plant.” Wikipedia, . 10 Feb 2014, 01:42 UTC. 11 Feb 2015, 20:08

Vascular plants have specialized tissues for conducting water, minerals, and photosynthetic products through the plant.
They include the ferns, club-mosses, horsetails, flowering plants, conifers and other gymnosperms.
Circulating resources through the plant allows it to grow to a larger size than non-vascular plants.

Xylem carries water and inorganic solutes up toward the leaves from the roots.

Phloem carries organic solutes throughout the plant.

Xylem and phloem 1

{ https://www.boundless.com/biology/textbooks/boundless-biology-textbook/plant-form-and-physiology-30/transport-of-water-and-solutes-in-plants-183/transportation-of-photosynthates-in-the-phloem-699-11924/ }

“Sucrose is actively transported from source cells into companion cells and then into the sieve-tube elements. This reduces the water potential, which causes water to enter the phloem from the xylem.”
“The resulting positive pressure forces the sucrose-water mixture down toward the roots, where sucrose is unloaded. ”
“Transpiration causes water to return to the leaves through the xylem vessels.”

xylem phloem 2

Seed plants – any plant that makes seeds

The spermatophytes, which means “seed plants”, are some of the most important organisms on Earth. …Soils, forests, and food are three of the most apparent products of this group.

Seed-producing plants are probably the most familiar plants to most people, unlike mosses, liverworts, horsetails, and most other seedless plants which are overlooked because of their size or inconspicuous appearance.

Conifers are seed plants; they include pines, firs, yew, redwood, and many other large trees.

Other major group of seed-plants are the flowering plants, including plants whose flowers are showy, but also many plants with reduced flowers – such as the oaks, grasses, and palms.

{ Univ. of California Museum of Paleontlogy, http://www.ucmp.berkeley.edu/seedplants/seedplants.html }


{excerpted from http://education-portal.com/academy/lesson/gymnosperms-characteristics-definition-types.html }

Gymnosperms were the first plants to have seeds.
They have naked seeds – as they do not have flowers
The seeds develop on the surface of the reproductive structures of the plants, rather than being contained in a specialized ovary.
These seeds are often found on the surface of cones and short stalks.

Characteristics of Gymnosperms

  • They do not have an outer covering (shell) around their seeds.
  • They do not produce flowers.
  • They do not produce fruits.
  • They are pollinated by the wind.






There are over 250,000 species of angiosperms. Angiosperms are flowering plants. They make up around 80 percent of all the living plant species on Earth.
   Flower Power

Angiosperms are vascular plants. They have stems, roots, and leaves.  Unlike gymnosperms such as conifers and cycads, angiosperm’s seeds are found in a flower.

Angiosperm eggs are fertilized and develop into a seed in an ovary that is usually in a flower. The flowers of angiosperms have male or female reproductive organs.


FlowerAngiosperms have to undergo a process called pollination before they can reproduce. Angiosperms have male sex organs called stamens.

On the end of the stamen is the anther.
This is where pollen is made.
The pollen has to be taken to the pistil or the female part of the flower.
The pollen is left on the stigma at the end of the pistil.
The stigma carries the pollen down a tube called the style to the ovary.

   The Birds and the Bees

HummingbirdAnimals like birds and insects can be pollinators.

When insects and birds get nectar out of a flower, they pick up some pollen as they move from flower to flower, and also can leave some pollen behind. Wind can also help move pollen from one flower to another.


Shasta DaisyAngiosperms in this group grow two seed-leaves. Their leaves usually have a single main vein that starts at the base of the leaf blade, or three or more main veins that spread out from the base of the leaf.

Most plants are dicots, including  most trees, shrubs, vines, fruit and vegetable plants and flowers. There are about 200,000 species of dicots.


OrchidThese angiosperms start with one seed-leaf.

The main veins of their leaves are usually unbranched.

There are about 30,000 species of monocots. Monocots include orchids, lilies, irises, palms, grasses, and grains like wheat, corn and oats. Fruits like dates and bananas also belong to this group.

– end angiosperm section –


2 types of seeds: monocot versus dicot

Let’s watch the two types sprout:
Grass (monocot) sprouting on left. The cotyledon remains underground and is not visible).
Compare to a dicot sprouting on the right.

{ http://en.wikipedia.org/wiki/Monocotyledon }


Let’s look at a diagram to see more details.

monocot v dicot seeds


What kinds of plants come from these different types of seeds?

Monocot plants versus dicot plants


monocot v dicot


Amniosperm versus gymnosperm

{ http://www.slideshare.net/vikkis/rhs-yea }

Gymnosperms vs angiosperms


Classification of plant life

{ http://www.easypacelearning.com/science/plants/plants/1332-plant-classifications-of-flowering-and-non-flowering-plants }


{ https://imanshomeschool.wordpress.com/2013/05/01/plant-classification-chart/ }


Plant reproduction



Sample questions

Feb 2017 MCAS.  A botanist studied two groups of rice plants to determine how they are related. Both groups of plants have similar shapes, but one group has longer stalks. When the botanist cross-pollinated plants from one group with plants from the
other group, the seeds produced did not sprout or grow. Which of the following conclusions is best supported by this information?

A. The two groups are the same species because the plants have similar shapes.
B. The two groups are different species because they have differently sized stalks.
C. The two groups are different species because the seeds produced cannot
sprout or grow.
D. The two groups are the same species because the plants were cross-pollinated and produced seeds.

Learning Standards

Massachusetts Science and Technology/Engineering Curriculum Framework

Life Science (Biology), Grades 6–8.
Classify organisms into the currently recognized kingdoms according to characteristics that they share. Be familiar with organisms from each kingdom.

Biology, High School
5.2 Describe species as reproductively distinct groups of organisms. Recognize that species are further classified into a hierarchical taxonomic system (kingdom, phylum, class, order, family, genus, species) based on morphological, behavioral, and molecular similarities.

Benchmarks for Science Literacy, American Association for the Advancement of Science

Students should begin to extend their attention from external anatomy to internal structures and functions. Patterns of development may be brought in to further illustrate similarities and differences among organisms. Also, they should move from their invented classification systems to those used in modern biology… A classification system is a framework created by scientists for describing the vast diversity of organisms, indicating the degree of relatedness between organisms, and framing research questions.

SAT Biology Subject Area Test

Evolution and diversity: Origin of life, evidence of evolution, patterns of evolution, natural selection, speciation, classification and diversity of organisms.

Teaching About Evolution and the Nature of Science, National Academy Press (1998)

Biological classifications are based on how organisms are related. Organisms are classified into a hierarchy of groups and subgroups based on similarities which reflect their evolutionary relationships. Species is the most fundamental unit of classification.

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