When is living things coming out

What does an animal need to survive? What does a plant need to survive? How are plant and animal needs different? The same? Are plants and animals both living things? Discuss how you could tell. Details Activity Length 30 mins. In this activity, students sort samples into living or non-living things.

Living components of a forest include: plants e. Objectives Describe the basic needs of living things Materials Pictures or samples of living and non-living forest components Key Questions What does an animal need to survive? What To Do Divide the class into small groups. When a leaf detaches from a tree, its cells do not instantly cease their activities. Does it die on the way to the ground; or when it hits the ground; or when all its individual cells finally expire?

If you pluck a leaf from a plant and keep its cells nourished and happy inside a lab, is that life? Such dilemmas plague just about every proposed feature of life. Responding to the environment is not a talent limited to living organisms—we have designed countless machines that do just that. Even reproduction does not define a living thing. Many an individual animal cannot reproduce on its own.

So are two cats alive because they can create new cats together, but a single cat is not alive because it cannot propagate its genes by itself? Consider, also, the unusual case of turritopsis nutricula , the immortal jellyfish, which can indefinitely alternate between its adult form and its juvenile stage. A jelly vacillating in this way is not producing offspring, cloning itself or even aging in the typical fashion—yet most people would concede it remains alive.

But what about evolution? During discussions about how best to find life on other worlds, Joyce and his fellow panelists came up with a widely cited working definition of life : a self-sustaining system capable of Darwinian evolution. But does it work? Let's examine how this definition handles viruses, which have complicated the quest to define life more than any other entity.

Viruses are essentially strands of DNA or RNA packaged inside a protein shell; they do not have cells or a metabolism, but they do have genes and they can evolve. Because of this constraint, he argues that viruses do not satisfy the working definition. After all, a virus must invade and hijack a cell in order to make copies of itself.

When you really think about it, though, NASA's working definition of life is not able to accommodate the ambiguity of viruses better than any other proposed definition.

Likewise, a virus has all the genetic information required to replicate itself, but does not have all the requisite cellular machinery. Both the worm and virus reproduce and evolve only "in the context" of their hosts.

In fact, the virus is a much more efficient reproducer than the worm. So if we use NASA's working definition to banish viruses from the realm of life, we must further exclude all manner of much larger parasites including worms, fungi and plants. Defining life as a self-sustaining system capable of Darwinian evolution also forces us to admit that certain computer programs are alive. Genetic algorithms, for instance, imitate natural selection to arrive at the optimal solution to a problem: they are bit arrays that code traits, evolve, compete with one another to reproduce and even exchange information.

Similarly, software platforms like Avida create " digital organisms " that "are made up of digital bits that can mutate in much the same way DNA mutates. These things replicate, they mutate, they are competing with one another. The very process of natural selection is happening there. He and many other scientists favor an origin of life story known as the RNA world hypothesis. In modern living organisms, DNA stores the information necessary to build the proteins and molecular machines that together form a bustling cell.

At first, scientists thought only proteins known as enzymes could catalyze the chemical reactions necessary to construct this cellular machinery. In the s, however, Thomas Cech and Sidney Altman discovered that, in collaboration with various protein enzymes, many different kinds of RNA enzymes—or ribozymes—read the information coded in DNA and build the different parts of a cell piece by piece.

The RNA world hypothesis posits that the earliest organisms on the planet relied solely on RNA to perform all these tasks—to both store and use genetic information—without the help of DNA or an entourage of protein enzymes. A geothermal pool in Wyoming.

Nearly four billion years ago, what we call life may have first evolved in similar "warm little ponds," as Darwin put it. Credit: Caleb Dorfman, via Flickr. Simple self-assembling membranes enveloped these early ribozymes, forming the first cells.

And proteins took on many catalytic roles because they were so versatile and diverse. But the cells of modern organisms still contain what are likely remnants of the original RNA world.

The ribosome, for example—a bundle of RNA and proteins that builds proteins one amino acid at a time—is a ribozyme. There's also a group of viruses that use RNA as their primary genetic material.

In the mids, Joyce and Tracey Lincoln constructed trillions of random free-floating RNA sequences in the lab, similar to the early RNAs that may have competed with one another billions of years ago, and isolated sequences that, by chance, were capable of bonding two other pieces of RNA.

By pitting these sequences against one another, the pair eventually produced two ribozymes that could replicate one another ad infinitum as long as they were supplied with sufficient nucleotides. Not only can these naked RNA molecules reproduce, they can also mutate and evolve.

The ribozymes have altered small segments of their genetic code to adapt to fluctuating environmental conditions, for example. Before he goes all Dr. Frankenstein, he wants to see his creation innovate a completely new behavior, not just modify something it can already do.

Evolution is a change in genes over time; one does not need to witness pigs sprouting wings or RNAs assembling into the letters of the alphabet to see evolution at work. The advent of blue eye color between 6, and 10, years ago—simply another variation of iris pigments—is just as legitimate an example of evolution as the first feathered dinosaurs.

Other questions to explore could be whether a computer which is turned on is alive; whether a hibernating bear is alive; and whether a deciduous tree in winter is alive. Consider listing key questions that arise in relation to this issue or review these ideas over time with students.

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