What is Animal: Definition and 123 Discussions

Animals (also called Metazoa) are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 micrometres (0.00033 in) to 33.6 metres (110 ft). They have complex interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology.
Most living animal species are in Bilateria, a clade whose members have a bilaterally symmetric body plan. The Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes, arthropods, and molluscs—and the deuterostomes, containing both the echinoderms as well as the chordates, the latter containing the vertebrates. Life forms interpreted as early animals were present in the Ediacaran biota of the late Precambrian. Many modern animal phyla became clearly established in the fossil record as marine species during the Cambrian explosion, which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified; these may have arisen from a single common ancestor that lived 650 million years ago.
Historically, Aristotle divided animals into those with blood and those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa (now synonymous for Animalia) and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between taxa.
Humans make use of many other animal species, such as for food (including meat, milk, and eggs), for materials (such as leather and wool), as pets, and as working animals including for transport. Dogs have been used in hunting, as have birds of prey, while many terrestrial and aquatic animals were hunted for sports. Nonhuman animals have appeared in art from the earliest times and are featured in mythology and religion.

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  1. G

    Animal sizes in low gravity environments

    "why size matters in animal behaviour? How can a hamster survive falling from the top of a skyscraper, ants carry over 100 times their own body weight and geckos climb across the ceiling? In the first of this year's Christmas lectures, Dr Mark Miodownik investigates . He reveals how the science...
  2. Eagle9

    How can we increase animal size?

    This is a continuation of my previous topic Is there any linkage between historic Oxygen levels in Earth's atmosphere and organism size? So, let’s forget about primitive organisms and turn our attention to higher ones, for example rodents, primates :oldsmile: Are there any genes discovered...
  3. F

    Gravity Fed Farm Animal Watering System

    I am trying to design/build a large self-filling drinking station, aka water bowl, for my goats and cow (see design attached). It's a takeoff of a dog's self-filling water bowl, i.e., uses gravity and vacuum to automatically refill the bowl as the water in the bowl is drank. The rain barrel is...
  4. SamRoss

    Is any form of animal torture OK?

    I've been deeply disturbed by recent brain-related experiments that involve driving around insects, rats, and probably other animals like remote-controlled toys. No doubt this will lead somehow to some benefit for humanity. To cut straight to the point, do you feel (because this is a moral...
  5. R

    What are animal reactions to death?

    This might be a little unsettling for some and I don't know exactly where to post this but here we go... What would the reaction of say a mother cat be in the moment if you where to take one of it's baby and kill it in front of them? Would they attack you? Would they show some signs of sadness...
  6. B

    Hard Wiring of Animal Behaviors

    I often hear that a certain behavior of an animal is "hard wired". I get the analogy, but what does that really mean in the brain? What two things are "wired" together and what is the actual "wire"? If a dog runs after a squirrel (dogs are of course "hard wired" to chase squirrels), are his eyes...
  7. TechTree

    Suitable plastic type for animal enclosure?

    Hello, So I've got a pet hamster which I'm trying to build an enclosure for. And so I was wondering what would be the most suitable type of plastic to use for the walls and floor. Obviously it's going to have the appropriate ventilation as the top and the front will be made entirely out of metal...
  8. T

    570 million year old animal life form

    Seems that us animals got an even earlier start than we thought. Short popular version: https://www.livescience.com/63289-ediacaran-leaf-fossil-is-animal.html Longer version: http://www.dailymail.co.uk/sciencetech/article-6043177/Animal-kingdom-OLDER-previously-thought-scientists-reveal.html...
  9. C

    Temperature change in a metal due to heat from a distant animal?

    In bolometers, incoming radiation warms a strip of material. this material will have a large thermal coefficient of resistance, leading to a (small) resistance change in the material. the inventor, Samuel Pierpoint Langley apparently used this to detect a cow from 1/4 of a mile away using a...
  10. I

    What is the largest size and weight an animal can be?

    Due to the square cube law there is a limit to how large an animal can be. I believe sea animals are capable of being much larger than land animals because the water supports their weight but what is the theoretical limit to how large a land animal can be and a sea animal? Excluding food...
  11. D

    Incredible displays of animal abilities

    As human beings, it's easy to look at other animals and imagine they are inferior to us in most ways. Sure, most animals are faster than us, but they run on four legs and we run on two. And most animals have far better hearing and smell, but we tend to have better eyesight. We don't have sharp...
  12. ORF

    Can a microorganism change the behavior of an animal?

    Hello. Can a microorganism change behavior of an animal? ( including humans). Thank you for your time. Regards, ORF
  13. M

    Non-caloric essential nutrients big vs small animals

    It is true that big animals contain more calories than small animals. However, are the figures for the content of essential nutrients that are not calories different? Such nutrients may be limiting factors and require foraging strategies that would be suboptimal from a simple calory point of...
  14. C

    What is the largest an animal can be?

    I know the blue whale is the largest known animal to have existed on Earth, but can animals conceivably grow larger, or is that pretty much the largest animal you can expect to find in the universe?
  15. Greg Bernhardt

    Drug 'reverses' ageing in animal tests

    http://www.bbc.com/news/health-39354628 Paper http://www.cell.com/cell/fulltext/S0092-8674(17)30246-5
  16. I

    Animal congregation catch-all title?

    Hello This might be a bit of an odd question, but is there a universal word that describes animal congregations? There are different types of congregations of course: http://www.animalsguru.com/animal-groups.html I know congregation is a description of the concept itself but I find the word to...
  17. Jamison Lahman

    Animal Intelligence Distribution

    My end goal is to extrapolate observed intelligences in the animal kingdom to determine whether or not it is statistically likely that a simulation argument is probable (though this could easily be used for the Fermi Paradox as well). Defining terms: "intelligence." Obviously all animals would...
  18. T

    How much could heaviest flying animal weight?

    OK I'm not sure if I put this in right subforum. I remember once reading in some science book by Isaac Asimov that the heaviest any flying animal can be is 22 kg, but I read on Wikipedia that Quetzalcoatlus may weighted up to 250 kg. So how come there's such a great difference in that...
  19. Eagle9

    Seeking free software for animal behavior tracking

    Good day guys :smile: I need to conduct the behavioral tests on rats. I need some free program for social behavior; the program should be able to track two rats simultaneously, their movement trajectories and time spent by these animals when they are close or far to each other (and to analyse...
  20. I

    Can DNA from an animal ever end up in bacteria or viruses?

    I was wondering if it is possible for a bacteria to enter a body and somehow get some amount of that animal's DNA in itself if and when it leaves the body? Or if it just continues to live in the body. Basically does DNA ever linger around? I heard about "DNA dropping" in organisms, if that's the...
  21. O

    Are eyes the only input to animal vision?

    We already know about echolocation, using the ears to sense objects and space around us (also dolphins, bats, whales and some birds are quite good at this).. But how about using a sensor on our tongue to input visual information. Here is a Scientific American article describing this technology...
  22. I

    Different animal sensory, short and long term memories?

    Is there any research that was done on animal long and short term memories? And short of empirical analysis, if there is none, is there much we could conclude, based purely on what we know about their brains? For example, from knowing which brain parts deal with explicit and which with...
  23. Graeme M

    Exploring Animal Communication: Is It Truly Possible?

    I have recently begun reading about human language and how it works. An obvious question that sprang to mind relates to efforts to communicate with other animals. I read Irene Pepperberg's book about her experiences with Alex the parrot, and I have seen video of interaction with Koko the...
  24. gracy

    Protein synthesis in an animal cell takes place

    protein synthesis in an animal cell takes place (a)in the cytoplasm as well as mitochondria (b)only on ribosome attached to nucleus (c)only in the cytoplasm (d)in the nucleolus as well as in the cytoplasm some sites suggest option (a)is correct and some site says option d is correct. Which is...
  25. gracy

    Difference between plant and animal cell

    A plant cell is usually larger in size. An animal cell is comparatively smaller in size. 2. It cannot change its shape. An animal cell can often change its shape. 3. A mature plant cell contains a large central vacuole. An animal cell often possesses many small vacuoles. 4. Plastids are present...
  26. E

    Identifying an Intriguing Insect: A Park Bike Ride Discovery

    I've been riding my bike in the park and I've noticed this guy passing by. It was of a hand palm size. Intriguing. Can you help me identify the insect?
  27. Y

    Was Darwin Wrong? [Wild Animal and Human Friendship]

    Does he failed to win a Darwin award ?. Try try again! So as you can see in this video: A Brave Man Hugs Young Bear Like His Son in the River... There's a fine line between being brave and being stupid.. In this instance we call him brave. Had the mother bear been in sight, we'd all be...
  28. Ganesh Ujwal

    Why we shouldn't eat already dead animal instead of killing

    Why we shouldn't eat already dead animal instead of killing & eat them? My Father told me that if we cook & eat dead animals we get unhealthy, that's why we should kill & eat them. did my father told correct answer?
  29. I_am_learning

    News Should the Gadhimai Animal Sacrifice Festival be Stopped?

    There is a animal sacrifice festival held every 5 years in Bara District in Nepal, attended by millions of people from India and Nepal. http://www.theguardian.com/world/2014/nov/28/mass-animal-sacrifice-nepal-festival-protests-gadhimai-hindu It is notorious for the large number of animals...
  30. enorbet

    Mechanism for Real "Zombies" in the Animal World

    Greetings I don't know if this is the right place to post this because I'm not certain how it is classified or if it can come under many headings. So please move this if it is better suited elsewhere. I watched a video on pbs.org a few years ago and since I am just now writing here about...
  31. Dembadon

    Dog w/out collar running around: called animal control

    Yesterday afternoon I noticed a dog running up and down our street, occasionally wandering through and around neighbor's yards. I'd never seen this dog being walked in the neighborhood before, so I went outside and got it to come into our back yard. I immediately noticed it didn't have a collar...
  32. K

    Calculating the range of an animal based on its movement costs

    Hi all, So I'm looking at how far an animal can move based on its basal metabolic rate and cost of movement. The total cost of these two is 45 Watts. It has 1.5 kg of food reserves with an energy density of 5.2 x 10^6 J per kg = 7800000 J of energetic reserves. All I want to do is see how...
  33. K

    Calculating the probability of an animal finding a resource

    I'd like some help working out the probability of my model animal finding water in a day. In my 'model' there is a square landscape 17km^2 The water pool is a circle of 500m radius (so approx 0.7854km^2) So in a one off shot the chances of hitting the water is 0.7854/17 = 0.0462 right...
  34. L

    Interspecies mating and animal classification

    I just read about how coyotes and dogs can interbreed, and their offspring can also breed. I thought one of the classifications of species was that two different species could either not breed together, or their offspring would be infertile. Dogs are of the species canis lupus, and coyotes are...
  35. T

    Can we design vehicle for animal self powered?

    Greeting. This is my first thread in engineering zone. Pleased to meet you all As the topic said. I want to ask about how possible to make animal powered vehicle for animal Or simply said, can we create bicycle for animal? I just think that, Human walk is low efficient compare to bicycle...
  36. turbo

    Can you rescue an animal in need?

    Lola was not the easiest addition to our home, but much easier than Duke. Duke had been abandoned and imprisoned in a shelter for about 5 months. He was clingy and emotional when my wife or I left, even for a short time. Lola has been with us for a few short days, and Duke has "adopted" her...
  37. turbo

    Do you have room for another rescue animal?

    It seems that we might get another rescue dog. The same woman (friend of my wife) who engineered our rescue and adoption of Duke is at it again. This time, the dog is a very young small-breed dog that the owner spent over $2K to buy and needs to be adopted because the owner must move. If she...
  38. totallyclone

    Using a stone to hunt down an animal with Centripetal Forces

    Homework Statement A bushman wants to hunt down a kangaroo so he uses a vine which is 2.0m long with a rock tied to the end of it. The bushman holds the other hand above his head which is 2.0m above the ground. The kangaroo observes that when the angle with the vine and vertical reaches 60°...
  39. DiracPool

    Animal Haters Unite - Vent Your Frustration Here!

    Yep, you heard that right. Animal haters thread. This is not to be confused with the insect (protostome) haters thead, which several of my, well, anyway... My beef is with the coming spring/sumer season, where all these &*%$#@*& dog owners like to let their noisy dogs disturb my...
  40. M

    If you could change yourself into just one other animal (not human),

    if you could change yourself into just one other animal (not human), what would that animal be? I chose a sea turtle. I love them and they are very pretty.
  41. K

    Animal Foraging Radius Equation Part 2

    Homework Statement I asked a similar question before relating to an animal's foraging radius. I think there was a typo but I'd like to show another example to see if I'm on the right track. The parameter values are as follows: Q= 5.2 × 106 J C = 1.5kg d= 0.055kg per hour k= 2.0...
  42. M

    Is it possible to power a freight train with an animal motor?

    The question is whether freight could be hauled along train tracks using only beasts of burden as a power source. My first ideas of a design involved tying, say, horses, to a belt which would drive a shaft, and, through simple gearing, provide power to push the train forward. The first few...
  43. G

    Physics concept that originated from an animal source?

    I need help finding some animals whose application of physics in the nature have inspired people to use the same physics in inventions/different applications. Some animals I've thought of are: Bats (Radar) Dolphins (Sonar) Birds (Airplanes) Bats (Radar) These animals would be...
  44. G

    Physics concept that originated from an animal source?

    I need help finding some animals whose application of physics in the nature have inspired people to use the same physics in inventions/different applications. Some animals I've thought of are: Bats (Radar) Dolphins (Sonar) Birds (Airplanes) These animals would be perfect, except...
  45. G

    Physics concept that originated from an animal source?

    I need help finding some animals whose application of physics in the nature have inspired people to use the same physics in inventions/different applications. Some animals I've thought of are: Bats (Radar) Dolphins (Sonar) Birds (Airplanes) These animals would be perfect, except...
  46. M

    Question about evolution of animal species

    Please explain something I don't understand about the evolution of animals that have sexual reproduction. I thought that being a separate species means an animal will have sexual intercourse resulting in fertile offspring only if the partner is of the same species. I shall cite the giraffe...
  47. F

    How Long Does It Take for 80% of Carbon-14 to Decay in a Dead Animal?

    Im having trouble answering this question. How long it takes for 80% of the carbon-14 to decay in an animal after it has died. Carbon decays rate 0.012% per year. So, my understanding is, -(R = 0.00012 yr-1, t=1 yr) R=Ro exp (-λt) 0.00012=Ro exp(-λ(1)) ---- (1) -No = 0.8...
  48. zoobyshoe

    Medical Dissonant music brings out the animal in listeners

    "Dissonant music brings out the animal in listeners" I don't know about this. Dissonance is effective because it reminds us of animal distress calls, but why are animal distress calls effective? Because they're dissonant, maybe?
  49. micromass

    Share Animal Pictures: For Animal Lovers

    Post your favorite animal pictures here!
  50. M

    Animal Brain size, mass, and surface area

    Animal Brain size, body mass, and surface area S.J. Gould wrote a series of interesting articles (chapters 22-24 in Ever Since Darwin) about the ratio of body mass to brain mass among animal species. Bigger animals have bigger brains (of course) but the ratio is getting smaller: a human's brain...