What's the Most "Animal" Animal? Crash Course Zoology #2

Summary

In this episode of Crash Course Zoology, host Rae Wynn-Grant explores the diversity of the animal kingdom, aiming to identify the 'most animal' animal. With an estimated 1.5 million known species and more to be discovered, the video discusses various zoological techniques to estimate global species richness. It highlights the significance of the phylum Arthropoda, particularly beetles within the order Coleoptera, as the most common type of animal. The script also touches on the potential for future discoveries to redefine our understanding of the 'mode animal'.

Takeaways

• 🌐 There are approximately 1.5 million known animal species, but many more remain undiscovered.
• 🧐 Zoologists study animal diversity to understand the life of most animals and the variations among them.
• 📊 The 'mean' animal concept is impractical due to the impossibility of averaging physical features across species.
• 🔍 The 'median' animal is challenging to identify due to uncertainties in the divergence timeline of animal groups.
• 🐛 The 'mode' animal, or the most common type, is a more feasible approach to represent the average animal.
• 🌿 Terry Erwin's study in 1982 estimated 30 million species of tropical arthropods using the diversity ratio technique.
• 🌱 The global species richness is estimated to be between 8 to 10 million species, based on various scientific methods.
• 🦋 Arthropods, particularly insects, are the most diverse and numerous animal group, making them strong candidates for the 'mode' animal.
• 🌎 Macroecological patterns and the species-area relationship help zoologists estimate global species richness.
• 🧬 DNA barcoding is a modern technique used to identify species and contribute to the understanding of global species richness.
• 🐞 Beetles, as part of the phylum Arthropoda, are considered the 'mode' animal due to their vast number of species and diverse habitats.

Q & A

What is the significance of finding the 'most animal' animal in zoology?

Finding the 'most animal' animal helps zoologists understand the common traits and behaviors of most animals. By identifying a species that best represents the majority of metazoans, researchers can make sense of the vast diversity in the animal kingdom and gain insights into how most animals live.

Why wouldn't calculating the average number of legs or eyes help in identifying the 'most animal' animal?

Averaging out features like the number of legs or eyes would result in unrealistic animals, like those with three legs. This method doesn't accurately represent how real animals live or function, making it unhelpful for understanding common animal traits.

What is the mode animal, and why is it important?

The mode animal represents the most common type of animal in terms of species numbers and characteristics. Studying the mode animal is important because it offers insights into the life and traits of the most prevalent animals, helping zoologists understand the majority of animal species.

How did Terry Erwin estimate the number of arthropod species in the tropics?

Terry Erwin used a diversity ratio technique by counting beetle species in a hectare of tropical forest. He calculated how many were host-specific and then extrapolated these numbers to estimate the total number of arthropods in the tropics, concluding there were 30 million species.

Why has Erwin's estimate of 30 million tropical arthropod species been recalculated over time?

Erwin's estimate has been recalculated because not all forests have the same number of tree species, and not all trees host the same number of unique beetle species. Improvements in methodologies, such as DNA barcoding and macroecological patterns, have refined these numbers over time.

How does DNA barcoding help zoologists estimate species richness?

DNA barcoding allows zoologists to compare genetic material across species, which can help identify unknown species or reveal that what was thought to be one species is actually two or more. This method provides a more precise way to estimate global species richness.

What is the phylum Arthropoda, and why is it considered highly successful?

Phylum Arthropoda includes over 1.1 million species, making it one of the most diverse and successful groups in the animal kingdom. Its members, such as insects, crustaceans, and spiders, have adapted to various habitats, allowing them to thrive across different environments.

What characteristics define beetles as the 'most animal' animal?

Beetles, as part of the largest group of arthropods, have six legs, three body segments, compound eyes, antennae, and a hard exoskeleton. They are highly adaptable, found in various habitats, and have evolved to fill many ecological niches, making them representative of the 'most animal' animal.

Why are chordates not considered the 'most animal' animal despite their popularity?

Chordates, which include fishes, mammals, and birds, are popular and well-known, but they only make up about 0.03% of all animals. In contrast, arthropods, particularly insects, are far more numerous and diverse, making them a better representation of the majority of animals.

Why might beetles not always remain the 'most animal' animal?

As zoologists continue discovering more species and exploring groups like nematodes and parasitic wasps, beetles may eventually be unseated as the 'most animal' animal. The discovery of more species could change our understanding of the most common traits in the animal kingdom.