Tag Archives: Animals

How do chicken eggs not crack inside their body?

Eggs can crack inside the hen, but it’s not common because eggs are actually pretty strong when forces are applied evenly over the entire shell.

If you wrap your whole hand around an egg trying to make as much surface contact as possible, it’s actually pretty difficult to break the egg by squeezing it. If you pinch the egg between two fingertips, it’s much easier because the force is concentrated on a smaller area of the shell.

Imagine pushing an egg on to the point of a sharpened pencil. It would pierce through pretty easily, right? Now imagine pushing an egg onto a soft ball of clay. It takes much more pressure to break it. So you can imagine if the insides of a hen are pushing on the egg evenly from all directions, it gets even more difficult.

How did sexual reproduction first develop in animals?

It is difficult to definitively say how it first came about, but there are some key factors that can be used to determine.

First, the main difference between sexual and asexual reproduction is that sexual reproduction “reorganizes” the parent DNA into a new pattern, while asexual is essentially the parent self-cloning. By being able to reorganize DNA, sexual reproduction had an advantage over asexual reproduction because it caused more mutations to occur in the DNA. This leads to a higher chance that a mutation will be beneficial to the organism, especially because the baby organism gets two sets of DNA to choose from, doubling its genetic resources. It also means that if one parent has a successful mutation that the other parent does not have, the baby organism will have a better chance at acquiring that mutation.

Second, we know that with two (or more) sexes, one sex must be more involved in the reproduction than the other. In most species, this is the female organism, which is able to do the reproductive work of bearing young. The male organism can merely contribute DNA, but does not actually bear young. With 50% of the population unable to make the babies, conditions must be good enough to allow the other 50% to reproduce often enough and quickly enough to maintain the whole species’ population. This means temperature, food sources, and safety from predators or environmental threats needed to be ideal.

We can break down the evolution of sexes a bit more; there is a term “anisogamy” which means reproduction with sperm and egg. This first evolved in tiny cells that contained only one set of chromosomes. Chromosomes are chains of DNA. When the cells would reproduce, the egg would provide one chromosome, and the sperm would provide a different chromosome. For a brief period, the baby cell would contain both chromosomes, and after a short period of development one of the chromosomes would “win” and that chromosome would become the DNA pattern that the new cell would eventually pass onto its own young.

This “anisogamy” developed when two compatible cells evolved, that were slightly different but able to mate with one another. In the first tiny cells that accomplished this, they were too similar to really be called “male” or “female,” but the difference was enough to spark the eventual evolution of male and female.

So, to recap:

Single cells would split in half to reproduce. Then, cells evolved a few changes, and this resulted in different types of cells that contained different sets of DNA. While some of these evolved cells eventually split off into entirely new species from the original cells, some others retained a special compatibility that allowed them to share their DNA, and they could mate with each other. Exactly how they started the ability to share the DNA (i.e. physically have sex, since they did not have vaginas or penises at that point) to make offspring is difficult to know for certain, but it may be similar to how some species of bacteria can “conjugate” or stick together to create new DNA combinations. A bit like the thing absorbing nearby cells and acquiring their DNA. So, the two new types of parent cells were able to provide not one, but two sets of DNA for their offspring to choose from. The offspring would typically end up with the most successful (dominant) DNA. This gave the offspring a better chance at surviving and reproducing, and this adaptation was so successful that it developed into fully fledged male and female versions of a single species.

How does hibernation work for animals? Does a hibernating animal stay in the same position for entirety of the winter?

There are many forms of hibernation, so not every animal that hibernates does so in the exact same way.

Some animals like bats, for example, sleep deeply and don’t wake up during hibernation; others such as marmots get up from time to time. Also they don’t sleep all the time, but wake up and then sleep again – they don’t stay in the same position, they might turn around and move arms and legs to be comfortable.

What they all have in common is that the hibernation initiates a very passive and reduced state. During the months or weeks of hibernation, the animals don’t eat, so their metabolism is reduced, their body temperature lowered, as is their heart and breathing rate. This is what makes hibernation different from normal sleep. It affects the whole body.

To wake up they need a lot of energy as the body fires up the “engines” again. If a hibernating animal is disturbed during hibernation and has to wake up often, it might die (it will starve during a hibernation phase as it does not have enough energy reserves to survive). The waking up process is also driven by hormones and can occur during hibernation if the animal gets disturbed or has to flee/move.

How complex are animal “languages”?

There’s a tremendous variety in the levels of intelligence and, alternately, cleverness, in various animals. This often translates directly to the complexity of their language. Same goes for pack behaviours: some are learned (e.g. lions hunting), some are purely instinctual (e.g. division of labour in termite nests).

And it’s important to realize that language is not limited to vocal elements. Body languages, smells/pheromones (particularly during mating seasons) and dances often contribute to communication between animals.

From available evidence it would appear that no form of animal communication comes anywhere near the complexity of human language.

Most insects don’t really communicate beyond the instinctual level. There’s no actual thought behind it, it’s just automatic. One of the more sophisticated communications is bees “dancing” the direction and distance of fields of flowers when they arrive at their hive.

Reptiles and amphibians have vocalizations that mostly announce their presence, although frogs can get into some pretty loud “hey this is my territory” duels during summer nights at the pond.

Fish are mostly instinct-type communicators. Some use visual signals and water pressure changes in schools, helping them to coordinate movement. A few vocalize. Squid and octopi can send visual signals to each other through changing the colour of their skin; some are thought to be as smart as dogs.

Birds are near the top of the list, with highly intelligent gray parrots being taught huge vocabularies of human words to the point where some can make their own sentences. As superb mimics, they have the advantage of being able to actually shape their communications to exactly match our own. Many other species have more limited vocabularies that they use among themselves, with word count ranging from a few basic calls for nighthawks to a high number of different coordinating communications for crows.

Then there’s mammals, and most use just basic words like wolf howls or happy barks to communicate. Some are even dedicated to crossing species; cats meow at humans but not so much when we’re not around. Cetaceans like dolphins and orcas and whales have very complex songs though, and a lot of fairly complex communication goes on between them. There’s a lot of non-verbal communication that happens in chimp tribes.

Wolves certainly do use communication to coordinate their actions. It’s not just vocal, but body language as well. They even appear to vote: if their leader wants to, say, go hunting, they might gather and then cast their votes by sneezing.

That’s a very sophisticated form of animal communication, but human language still knocks it clean out of the water. We can talk about abstract things, we can talk about things happening in different places or at different times, we can even talk about things that haven’t happened yet or may never happen at all. By contrast, animals appear only to be able to communicate things that are happening here and now.

Another feature of human language is that it is “open-ended” and “productive”. This means that although we only have a finite number of symbols (sounds and gestures that make up the language), we can talk about an infinite number of things, including things nobody has ever talked about before. Animals by contrast can only talk about a finite number of things: they can say, “I am hungry,” but they can’t say, “A rose by any other name would smell as sweet.”

There are claims – and they are very controversial claims – that primates can be taught to communicate with humans in ways that mimic human language. The most famous is Koko the gorilla, who has been taught American Sign Language. The researchers working with her claim that she can not only talk about things that happened in the past, she can even make up her own phrases (for example, signing “dirty bad toilet” as an insult). But some linguists are skeptical of these claims, saying that the signs Koko produces are so vague and poorly executed that you can’t tell what, if anything, they mean.

Why some animals seem to enjoy human affection?

Some animals are social animals. In the wild they would live in packs, herds, or groups. We domesticated some of these animals and we become their pack members or herd members. They want attention and since humans give it to them (and give them food also) they bond to us.

Not all animals that live in packs can be domesticated and behave too wild as they mature so we don’t keep them as pets or livestock.

Noting that when these animals which seem to enjoy our attention are not raised by humans (but live wild/feral) they don’t crave human attention at all and instead find companionship with other wild animals of their own kind. Wild horses will run from people, feral dog packs will even attack people. Feral cats will run away from people.

Why are jellyfish kept in a tank without any plantation or soil at all?

Jellyfish are very delicate and extremely hard to keep in tanks for that reason. They are mostly water with very thin membranes as their body structure. Any sharp object can rip them apart fairly easily. Of course, there are lots of larger jellies that have evolved to be more durable, or can grow big enough to withstand damage (like the Stygiomedusa gigantea, or the larger fried egg jellyfish specimens). But the vast majority are small and mostly helpless, except for their unique stinging cells, but that doesn’t affect their ability to survive in a tank.

In their natural environment, they usually just float freely with the currents in the open ocean, so there’s nothing for them to bump up against (except predators). They aren’t strong swimmers either, so they can get stranded or trapped easily if the current washes them onto the shore or pushes them into a confined area.

In order to most closely replicate their natural environment, jellies need tanks with rounded edges to keep from getting stuck in corners, a gentle current to propel them around the tank, and a small amount of food suspended in the water. They have very specific requirements for temperature and water pH too. No gravel since they could scrape against the grains and tear up their membranes. No plants since they could get stuck in the leaves.

How do predators eat poisonous spiders and not die?

Poisonous and venomous are different things. Poisonous things may kill you if you eat them, and venomous things may kill you if they bite you.

To be specific, these spiders are venomous which means the toxin is intended to be injected into the tissues of the unlucky victim.

In some cases, venom does not achieve the same impact if ingested. They may be diluted in the stomach, less able to penetrate to the tissues where they can do harm, and the hostile environment may even break down the critical substances that give the venom its potency.

How is the mating ritual of octopus?

Nature is full of wonders and strange things that will blow our mind if you look closely enough. The animal kingdom particularly has many bizarre things most of us are yet to know. The mating ritual of octopi is one such thing we would have a hard time to believe, let alone understand.
There are estimated to be around 300 species of octopi, or octopuses. Many of them are highly intelligent as well, capable of solving mazes and imitation. They have a lifespan of from three to five years. Except some variations, the mating of all the species is almost alike. As you know, octopi have eight long arms. The water creatures can squeeze through tight spaces due to lack of bones. And it is one of these arms that plays a significant role in the mating, at least in the cases of male octopi.
You can say that the mating of octopi is a subdued and mechanical affair. When the female octopus is ready to mate, she releases the equivalent of pheromones which attract males. The male octopus has a special arm called hectocotylus in which spermatophores, or packets of sperm, are stored. In most species, it is the third arm. The male transfers the sperm packets using hectocotylus to the mantle of the female. In some species, the male detaches its entire arm and would give it to the female. The female stores the sperm (or the arm) until she is ready to lay eggs. At the time of laying eggs, she would spread the sperm over them and fertilize them. The number of eggs vary from species to species, and can go up to 200,000. The eggs take between two to ten months to hatch, and the female cares them well, even avoiding food. She sometimes blows water on the eggs to keep them clean and to ensure oxygen supply. Upon hatching, the newborns are on their own and feed on small planktonic creatures. Only a tiny fraction of them would survive the predators and make it to the adult stage, to start another cycle of reproduction.
The octopuses don’t survive the mating for too long. The male dies soon after the mating while the female dies after the hatching of eggs. Scientists have recently discovered that the females of some species suffocate the males to death immediately after the mating, for reasons unknown. More research is going into this phenomenon.

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How do fish’s gills work? And why do fish die when taken out of water?

Like any of the animals on land, fishes also need oxygen to power their metabolism and survive. However, they don’t get oxygen freely like we do on land. They use the oxygen contained in the water for that, employing the gills to exchange the oxygen and carbon dioxide. The gills are to fishes what lungs are to humans and other land animals. They need to absorb the oxygen in water and emit the carbon dioxide produced as a byproduct of the body activities. And the gills have a major role to play in that process.

Click to enlarge

The gills are essentially tissues made up of filaments, long chains of proteins. These filaments have a large network of capillaries and provide a wide surface area that helps the exchange of gases and ions. The gills are located on both sides of the pharynx of fishes. They help to absorb the low level of oxygen in water while also regulate the level of sodium chloride and other minerals in blood. The capillaries in gills are made of tissues called epithelium.
Gills work based on the same principle of lungs, although it employs a special kind of pumping mechanism to take in the oxygen dissolved in the water.
While breathing, the fish gulps a mouthful of water. Then it draws the sides of its throat together, forcing the water through the gill slits, so that it passes over them to the outside. At the same time, the heart will be continually pumping deoxygenated blood from various parts of the body into the gill ļ¬laments. When the oxygenated water passes along the deoxygenated blood, oxygen diffuses into the gills and is taken into the bloodstream while the carbon dioxide diffuses into the water which will go out through the gills.
In most of the species, this process is made easy with the use of a countercurrent exchange system in which blood and water flow in opposite directions to each other. The fish can extract around 70% of the oxygen dissolved in the water through this means. The surface area of the gills is instrumental in this process. Since, the oxygen content in water is twenty-five times less and the diffusion rate of oxygen is 10,000 times slower than that in the air, this high surface area is important to keep the mechanism running effectively.
The constant flow of water through the gills is a must for this process. If there is no water, the gills will collapse and stick to each other, making the diffusion of oxygen impossible. This is what happens when a fish is taken out of water and why the die.

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Why is chocolate poisonous to dogs?

Chocolate is one of the most favorite delicacies for the people around the world. Everyone loves to have a taste of the sweet, thick food. However, many of you might have heard chocolate is harmful for dogs. Isn’t it rather puzzling? Why a substance harmless to humans would be harmful to dogs?
Actually chocolate is harmful to humans as well. It is just that the effect of them on us is considerably less than on others, particularly dogs. It is down to the difference in biological mechanisms of humans and dogs. The toxic effect of chocolate is attributed to a chemical contained in it, called theobromine. It is a stimulant similar to caffeine, found in cocoas, tea and cola beverages. The amount of theobromine varies according to the different types of chocolate. Dark chocolate contains larger amount of the chemical than the white chocolate or milk chocolate. The dark chocolate contains around 15 grams of theobromine per kilogram while more refined chocolates contain around 2 grams.
The impact of the chocolate on a dog depends on the type and amount of the chocolate consumed by them and the dog’s body weight. Dogs and other domestic animals metabolize theobromine more slowly than humans. The theobromine is toxic to a dog when the amount of it rises to around 150 milligrams per kilogram of the body weight of the animal. That is if a dog weighing 30 kg has consumed 4.5 g of theobromine, its body would suffer from serious effects. The median lethal dose of theobromine in dogs is about 300mg/kg. In humans and rats, this is near 1000 which makes them less prone to the effects of theobromine.
The important body parts that theobromine affects are heart, central nervous system and kidneys. The biological half-life of theobromine in dogs is 17.5 hours. The symptoms will begin to show from four hours to one day after the dog has consumed chocolate.
The symptoms vary according to the amount of the theobromine that entered the body. The dog will start to display the signs of discomfort including but not limited to vomiting, increased urination, diarrhea, restlessness and hyperactivity. The theobromine could be fatal to dogs, leading to seizures to internal bleeding and heart attack, and eventually death.
There is no antidote to theobromine poisoning. The best treatment is to make the dog vomit and clean its stomach within a few hours of chocolate consumption. The vets will also give medicines for seizures. With prompt intervention, the dog can be saved.

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