science

Rosids

Rosids is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rosids rather than just read about it. In short: The rosids are members of a large clade (monophyletic group) of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms. The clade is divided into 16 to 20 orders, depending upon circumscription and classification.

Key takeaways

Rosids belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rosids to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rosids from memory before moving on to harder problems.

Reference excerpt

The rosids are members of a large clade (monophyletic group) of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms. The clade is divided into 16 to 20 orders, depending upon circumscription and classification. These orders, in turn, together comprise about 140 families. Fossil rosids are known from the Cretaceous period. Molecular clock estimates indicate that the rosids may have originated in the Aptian or Albian stages of the Cretaceous, between 125 and 99.6 million years ago. Today's broadleaved forests are dominated by rosid species, which in turn help with diversification in many other living lineages. Additionally, rosid herbs and shrubs are a significant part of arctic/alpine and temperate floras. The clade also includes some aquatic, desert and parasitic plants.

Name The name is based upon the name "Rosidae", which had usually been understood to be a subclass. In 1967, Armen Takhtajan showed that the correct basis for the name "Rosidae" is a description of a group of plants published in 1830 by Friedrich Gottlieb Bartling. The clade was later renamed "Rosidae" and has been variously delimited by different authors. The name "rosids" is informal and not assumed to have any particular taxonomic rank like the names authorized by the ICBN. The rosids are monophyletic based upon evidence found by molecular phylogenetic analysis.

Relationships The rosids and Saxifragales form the superrosids clade. This is one of three groups that comprise the Pentapetalae (core eudicots minus Gunnerales), the others being Dilleniales and the superasterids (Berberidopsidales, Caryophyllales, Santalales, and asterids).

Classification Three different definitions of the rosids were used. Some authors included the orders Saxifragales and Vitales in the rosids. Others excluded both of these orders. The circumscription used in this article is that of the APG IV classification, which includes Vitales, but excludes Saxifragales. Thus, the rosids consist of two groups: the order Vitales and the eurosids. The eurosids, in turn, are divided into two groups: fabids (Fabidae, eurosids I) and malvids (Malvidae, eurosids II).

Orders The rosids consist of 17 orders. In addition to Vitales, there are eight orders in fabids and eight orders in malvids. Some of the orders have only recently been recognized. These are Vitales, Zygophyllales, Crossosomatales, Picramniales, and Huerteales.

Phylogeny The phylogeny of rosids shown below is adapted from the Angiosperm Phylogeny Website.

The nitrogen-fixing clade contains a high number of actinorhizal plants (which have root nodules containing nitrogen fixing bacteria, helping the plant grow in poor soils). Not all plants in this clade are actinorhizal, however.

References

External links Media related to Rosids at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Rosids

Start with the simplest possible case. Write down what Rosids claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rosids before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rosids ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rosids

In research: Rosids appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rosids in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rosids is common in secondary-school and first-year university syllabi. It links to neighbouring topics Extant Cretaceous first appearances, Plant unranked clades, Rosids, so understanding it makes those chapters shorter.
In everyday life: Look for Rosids outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Rosids in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rosids means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rosids out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rosids in simple terms?

Why does Rosids matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rosids?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rosids.