Hour: 1, 2, 3, 4, 5, 6, 7
How to Read a Cladogram:
A cladogram is a tree-like diagram showing evolutionary relationships. Any two branch tips sharing the same immediate node are most closely related. All taxa that can be traced directly to one node (that is they are "upstream of a node") are said to be members of a monophyletic group.
A cladogram is a diagram much like a family tree showing the phylogenic tree of different species and demonstrating where they evolved from common ancestors. Once taxonomists based cladograms on physical, easily-observed characteristics; today, they can use more reliable information like genetic and biochemical analysis to determine the relationships between different species.
Each branch on a cladogram is referred to as a "clade" and can have two or more arms. Taxa sharing arms branching from the same “clade” are referred to as "sister groups" or "sister taxa." Synapomorphies are characteristics shared by the taxa branching from the same clade, but not shared by taxa on other branches – for instance, vertebrates share certain synapomorphies that are not shared by invertebrates.
The two basic principles behind assembly of a cladogram are that the process from ancestor to descendant should be shown as simply as possible in the tree; and the taxonomic categories applied to the branches in a clade should be monophyletic, or cover an ancestor and all its descendants. Cladograms should not be seen as evolutionary fact, but only as a possible path for speciation.
Plant evolution / Cladograms:
When biologists look at a new plant, there are many factors they need to take into account to classify it into the proper category. They need to look at it different characteristics such as: Does it live in water or on land? Does it have a vascular system?Or is it an angiosperm or gymnosperm? A cladogram may help them compare these evolutionary relationships.
The plant kingdom
Remember organisms are broken down into six kingdoms; archaea, bacteria, protist, plants, fungi and animals. In the kingdom “Plantae”, some biologists group green algae (Chlorophyta) together with land plants in one large kingdom, called Viridiplanae ("green plants").
See if you can answer the following questions about the provided cladogram.
Cladogram: Plants and their relatives
1. Green plants (viridiplntae) break down into what 2 groups.
2. In land plants which of the two taxa (groups) is the oldest?
3. What vascular plant came next?
4. Looking at the chart, what type of plants occurred next?
5. Explain the difference between the following terms:
a. Vascular and non-vascular plants:
b Angiosperm and Gymnosperm:
Once you have completed this worksheet see the instructor to check your answers with the answer key.
How to Read a Cladogram: Answer Key
1. Green plants (viridiplntae) break down into what 2 groups.
Green algae and land plants.
2. In land plants which of the two taxa (groups) is the oldest?
Non-vascular plants
3. What vascular plant came next?
Vascular, non-seed plants.
4. Looking at the chart, what type of plants occurred next?
Seed plants
5. Explain the difference between the following terms:
a. Vascular and non-vascular plants:
Vascular have a network of tube (Xylem and Phloem) that move water throughout the plants, which allows them to grow taller
Non-vascular, the water / minerals ooze from one cell to the next. Non-vascular plants are low to the ground and need to be around
moist conditions.
b Angiosperm and Gymnosperm:
Angiosperms are flowering plants
Gymnosperms are Cone bearing plants.
c. Monocots and Dicots:
Monocots – 1 cotyledon, fibrous roots, vascular bundles scattered, flower
petals in multiples of 3’s, parallel veins in the plant’s leaves.
Dicots – 2 cotyledon, taproot, vascular bundles in rings, flowers petals in multiples of 4 & 5’s, branched veins in the plant’s leaves.