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High school biology - NGSS
Course: High school biology - NGSS > Unit 8
Lesson 1: Natural selection and adaptationNatural selection and adaptation
Natural selection leads to adaptation, that is, to a population dominated by organisms that are anatomically, behaviorally, and physiologically well suited to survive and reproduce in a specific environment. That is, the differential survival and reproduction of organisms in a population that have an advantageous heritable trait leads to an increase in the proportion of individuals in future generations that have the trait and to a decrease in the proportion of individuals that do not. Created by Khan Academy.
Want to join the conversation?
- Hey, does anyone know some examples of some of those parasitic wasps mentioned at? 8:20(5 votes)
- Most parasitoid wasps look like flying black ants. Usually, you could find them in your backyard in spring and summer. Mostly they lay their eggs on caterpillars, beetles, aphids, etc. Stunning the host while laying their eggs. The host lives as the wasp larva feed and grows inside. Even parasitoid wasps might be a bit gross they are very beneficial in reducing the pest population.
Hope this helped!(8 votes)
- how do the bees contain solar panels?(5 votes)
- It’s not actual solar panels, but it works kind of like one, like he said, it’s from natural selection making species change, however I’m not too sure what exactly let’s them do that.(3 votes)
- so will fish eventually get laser eyes?(4 votes)
- Mabey but to get laser eyes that do damage the fish would need to have a reflective chamber than magnifies ligth about 1000x as much(2 votes)
- atwhy does the fish look like a science experament gone wrong 6:33(4 votes)
- pecause it is(1 vote)
- So natural selection causes variation and adaptations and these variations and adaptations are caused because of genetic changes/mutations, meiosis, sexual reproduction for certain types of adaptations, but environmental circumstances is what causes behavioral adaptations to happen? because a change in the environment causes populations of the same species, but in slightly different situations (Eg. environment) causes organisms to act differently like with the honey bee example?(3 votes)
- … isn’t the leaf and caterpillar blue though?(1 vote)
Video transcript
- [Dr. Samuel] Hi
everybody, Dr. Samuel here, your friendly neighborhood entomologist. And I was hoping that we
could take a few minutes to talk about adaptation. What comes to mind when
you think about adaptation? You might think of cryptic morphology that helps organisms hide from predators, scaly armor or spines to
protect organisms in a scuffle, or increased melanin
pigmentation in the skin to shield an organism
from the damaging impacts of harsh sunlight in really sunny areas. And if this is the sort of
thing that you thought of, you're right, these are all adaptations. But what people often
miss about adaptations is that they all help
organisms survive and reproduce in a particular environment. The word adaptation can refer to a trait that makes an organism more
suited to its environment. But it can also mean the process by which a population becomes dominated by organisms that are suited to their environment. The point is that adaptation
happens in a population as its organisms accumulate adaptations. And this all happens through the process of natural selection, which you may have heard about. With natural selection, we see organisms with beneficial heritable traits, increasing their share of the
gene pool in the population because they're more likely
to mate and produce offspring. This means these well-adapted
organisms have higher fitness, a measure of an organism's ability to survive and reproduce in its specific environment. These traits or adaptations
make the organisms better suited to survive and reproduce because they're better suited to the specific environmental
context that they live in. That is our green caterpillars blend in, and thus, survive better
on the green leaves, and the orange caterpillars
on the orange leaves. As you can see, natural selection is intimately intertwined
with the environment in which it takes place. And this is why natural
selection can lead to adaptation. Even the concept of adaptation is diverse. Adaptations can be anatomical, changes to physical
structures, or physiological, changes in the function
of these structures, or adaptations can be changes to behavior. We see this with honeybees
adapted to life in Africa, sometimes called by the suboptimal names, Africanized honeybees or killer bees. They're the same species
as and look identical too. Populations of honeybees
adapted to North America, but their behaviors diverge dramatically. Because the African populations are adapted to life in a
hot, tropical environment, sometimes, they construct nests
right out in the open air, nests in open air. This is extremely rare for populations adapted to the temperate
climate of North America, where the temperature
range is far too broad between winter and
summer for open air nests to be successful. So, North American honeybee populations much prefer to live inside
of protected structures like inside of the trunks of hollow trees or the boxes that beekeepers provide, nests in protected structures. And in Africa, there are also more
large, fearsome predators interested in getting into the bees' nest. So, the frequency of traits
related to hyper defensiveness is much more common than in populations
adapted to North America, where there are fewer
aggressive predators, heightened defensiveness, low to moderate defensiveness. The success of honeybees
adapted to life in Africa left a lot of people worried that they would be similarly
successful in North America and replace the honeybees there. But those concerns ignored the connection between adaptation and the environment. Traits that helped those
bees survive in Africa and even helped them
in similar environments found in many regions of tropical, South and Central America, well, those same exact traits were liabilities in much of North America. Okay, so, this is all fascinating, but you may be wondering, if natural selection is
passing out adaptations, why doesn't it choose better stuff? Fish tend to get eaten
by birds and bears a lot. And that's gone on for
literally millions of years. So, why I haven't fish populations developed something like
laser eyes or teleportation? Instead, when a population
of fish does evolve defense, it's typically something like a few bones, that it already has,
getting longer and sharper and protruding out of their fins, like in the case of the
three-spined stickleback fish. These spines protect the stickleback from birds and other predators, but only if the spines are long enough to make it difficult for
that specific predator to swallow them. Birds with wider throats
are still able to eat even fully grown fish with
fully elongated spines. Laser eyes really do seem like
they would be more effective. It's almost like natural selection is just tinkering with
whatever it has lying around instead of going out
and buying something new and perfectly suited to the task. And that is exactly what's happening. Populations don't adapt by
accessing a bottomless well of awesome problem-solving options. Quite the contrary, with
natural selection as the driver, adaptations can be pretty limited. You might already be
tracking with the idea that if an increase in fitness is what natural selection is after, you don't need an adaptation
that allows you to incinerate all of your enemies. You just need one good enough
to solve whatever problem is keeping others in your population from surviving in mating. If that's a kingfisher
bird eating the other fish, the resolution might be just a spine that's only a half a centimeter longer than the other fishes. That's the reason why we see adaptations that look like natural
selection just grabbed whatever happened to be
lying around and modified it because it kinda did. A turtle's remarkably protective shell may look fancy and novel, but it's literally the
turtle's overgrown ribs fused with its spine. A narwhal's face spear, that there is just a tooth that grew all the way out of its face. Natural selection only has the options currently in the genes of a population with the occasional addition of new genetic sequences through mutation to work with when a problem arises. And you might be thinking, "Oh great! Mutations, those will help! That's how my favorite
superhero got her powers." Well, unlike what we see in movies, most mutations either have no real effect or result in problematic gene expression or nonfunctional proteins which is pretty bad
news for living things. So, adaptations are not
likely to be super weapons that ensure survival in all circumstances. Instead, they're useful traits that help increase an organism's fitness as the environmental
conditions apply pressure. So, adaptation is a remarkable system, but one with some pretty
pronounced limitations. Natural selection has to work
with what an organism has. But consider for a moment
what it has given us despite those limitations. Pistol shrimp have the ability to slam their claws shut so quickly that the water around them
collapses in on itself. It implodes knocking
nearby fish unconscious. Some honeybees can bundle together and vibrate their flight
muscles so rapidly that they can create a
biological convection oven which can cook predators to death. And there are parasitic wasps that have evolved to live
inside of parasitic wasps that live inside of parasitic wasps that live inside of caterpillars, like tiny, strange, little
Russian nesting dolls. And don't even get me
started on the hornets that have yellow patches on their abdomen that absorb solar energy to supplement the energy
provided by their diet. They have solar panels! I'd say natural selection has
done pretty well for itself.