Sex cells, or gametes, are different in that they take each set of chromosomes from the mother and father, duplicate them, and then swap them around before they break up and form four different cells. Each of these cells has just one set of chromosomes a mix of mother's and father's , instead of two identical sets like other cells throughout the body. When both an animal's parents are of the same species, the creation of sex cells goes smoothly: Both parents have the same set of chromosomes, so switching out the father's eye color chromosome for the mother's, for instance, doesn't cause any problems.
However, when the animal's parents are from different species, their chromosomes don't match up in order. So, for example, during the creation of sex cells when chromosomes get swapped, an eye color chromosome might get exchanged with a paw size chromosome, the video explains.
The video discusses a few rare cases in which female mules have been able to mate using only their mothers' DNA, spawning offspring that are also genetically their half-siblings. When one species contains some of the genes of another species, it is known as introgression. This is a powerful evolutionary force, because these new genes may code for new traits or behaviors that could help the parent species [ 5 ]. So far, we have only spoken about hybrids created by humans.
Lions and tiger never meet naturally in the wild, but other hybrids do occur naturally. In fact, there are hundreds of hybrids in the natural world. It is thought that one in four plant species, and one in ten animal species, hybridize [ 6 ]. Hybridization can help parental species by transferring new genes, through introgression, and can even lead to the creation of new species [ 5 ].
For example, South American Heliconius butterflies have gained part of their beautiful wing patterns through hybridization Figure 3 [ 7 ]. Heliconius butterflies use their wing patterns to attract mates, as well as to avoid predators, who interpret the patterns as warning signals.
Ancient hybridization of sunflower species has also generated new species in North America. These hybrid-origin sunflowers can live in more extreme environments, where the soil is poor or toxic. Hybridization combined traits of the two parent species, forming a new gene combination in the hybrid that enabled it to live in this new habitat [ 8 ].
Although many of the natural hybrids we have spoken about are from modern species, there are also examples of ancient hybridizations that happened tens of thousands of years ago. These hybrids can be identified even when the parental species are extinct. This is because some of the parent species genes will still be present in a small percentage in the hybrid. Using this method, an ancient hybrid was found to be an ancestor to many species of clownfish like Nemo from Finding Nemo.
Just like the sunflower, the combination of adaptations in this ancient hybrid allowed the clownfish ancestor to live in a new habitat [ 9 ]. As a result, this ancient hybrid is an ancestor to many modern clownfish species. Sometimes hybrids can be bad for the parental species and for the natural world.
If hybrids are very successful, there may be so many hybrids that they compete with their parent species for food and living space, which could lead to the extinction of the parent species. Losing a species is bad for biodiversity and can affect other species in that habitat. When this species loss occurs naturally, scientists do not try to stop it, because it is a natural process. Loss of a parent species due to hybrid offspring is only problematic when the hybrid is created by humans and introduced to an area where the parent species were not naturally found.
We must act to prevent the extinction of the parent species in these cases. But do not worry, the hybrids that we buy at the grocery store are unlikely to cause severe environmental harm, because there are rules in place to make sure they are grown with great care. Hybridization is a complex process involving the mixing of two species. Hybridization is an important part of evolution, due to the transfer of genes through introgression and its role in the generation of new species.
It is also part of our daily lives and is used to help improve foods and livestock. Not all scientists agree on how to define what separate species are. Lots of mutations occur between species. Infertile is the opposite, meaning the inability to have babies. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Wheeler and R. These exotic species now may encounter and mate with the native animals.
Many hybrid animals are sterile. For example, mules are the hybrid offspring of horses and donkeys. Only a horse mating with a donkey can make another mule. Biodiversity is a measure of the number of species. If many hybrids were produced, the two parent species could merge into one.
That would reduce the variety of species. But hybridization sometimes can boost biodiversity. A hybrid might be able to eat a certain food that its parent species cannot. Or maybe it can thrive in a different habitat. Eventually, it could become its own species, like the golden-crowned manakin. And that would increase — not decrease — the variety of life on Earth.
Hybrids can be different from their parents in many ways. Appearance is just one. Delmore wanted to know how hybrids might behave differently than their parents. Over time, this species has split into subspecies. These are groups of animals from the same species that live in different areas.
However, when they do encounter each other, they can still breed and produce fertile young. One subspecies is the russet-backed thrush, which lives on the west coast of the United States and Canada.
As its name implies, it has reddish feathers. The olive-backed thrush has greenish-brown feathers and lives farther inland. But these subspecies overlap along the Coast Mountains in western North America. There, they can mate and produce hybrids. One difference between the two subspecies is their migration behavior. Both groups of birds breed in North America, then fly south in winter. But russet-backed thrushes migrate down the west coast to land in Mexico and Central America.
Olive-backed thrushes fly over the central and eastern United States to settle in South America. Which directions do hybrids get? To investigate, Delmore trapped hybrid birds in western Canada. She placed tiny backpacks on them. A light sensor in each backpack helped record where the birds went.
The birds flew south to their wintering grounds, carrying the backpacks on their journey. The next summer, Delmore re-captured some of those birds back in Canada.
The length of the day and timing of midday differs depending on location. They flew somewhere down the middle. These treks, though, took the birds over rougher terrain, such as deserts and mountains. That could be a problem because those environments might offer less food to survive the long journey. But that strategy might also cause problems. Normally, birds learn cues on their way south to help them navigate back home. They might notice landmarks such as mountains.
But if they return by a different path, those landmarks will be absent. One result: The birds migration might take longer to complete. These new data might explain why the subspecies have remained separate, Delmore says.
Following a different path may mean that hybrid birds tend to be weaker when they reach the mating grounds — or have a lower chance of surviving their yearly journeys. If hybrids survived as well as their parents, DNA from the two subspecies would mix more often.
Eventually these subspecies would fuse into one group.
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