What is an Animal?When you think of “animals”, what pops in your mind? Lions and tigers and bears, oh my!
• But would you think of a sponge???• The natural sponges that people use for washing are the remainsof an animal• Animals come in manyshapes and sizes• Some are too small to be seen without a microscope and others are bigger than a school bus• They are all part of the animal kingdom
Animal Diversity• Look at this picture. How many animals do you see?
• You may be surprised to learn that feather stars and corals are animals• Spiders, fish, and birds are also animals• And slugs, kangaroos, and monkeys are animals, too• Scientists have identified more than 1 million species of animals• Scientists believe that more than 3 million species of animals live on Earth, and most have not yet been named
Vertebrates• Vertebrate: an animal that has a backbone• Includes fish, amphibians, reptiles, birds, and mammals• Humans are one of about 5,000 species of mammals
Invertebrates• You are probably more familiar with vertebrates than invertebrates, but vertebrates are definitely the minority among living things• Less than 5% of known animal species are vertebrates• Most animal species are insects, snails, jellyfish, worms, and other invertebrates
• In fact, beetles make up morethan 30% of all animal species!
Animal CharacteristicsAll animals share characteristics that set them apart from all other living things:1. Multicellular Makeup: – All animals are multicellular, which means made up of many cells – Eukaryotic, which means they have a nucleus – Animal cells do NOT have a cell wall – Surrounded only by cell membranes
2. Reproduction and Development – Almost all animals reproduce sexually – These animals make sex cells: sperm and egg – When egg and sperm join, they form the first cell of a new organism, which then divides into many cells to form an embryo – Embryo: an organism at an early stage of development – Asexual reproduction- hydra reproduce by budding
3. Many Specialized Parts – Animal’s body has distinct parts that do different things – When a fertilized egg cell divides into many cells to form an embryo, the cells become different from each other – Some cells may become skin cells, muscle cells, nerve cells, or bone cells – These different kinds of cells form tissues, which are collections of similar cells – Tissues then form organs
– Organ: group of tissues that carry out a special function of the body– Your heart, lungs, and kidneys are all organs
4. Movement – Most animals can move from place to place – They may fly, run, swim, or jump – Nearly all animals use movement to search for food, shelter, or mates at some stage in life – Can be less active during certain stages sea anemones swim through ocean while young, then cling to rocks as adults
5. Consuming • Animals cannot make their own food • All animals survive by eating other organisms or parts and products of other organisms • Animals are consumers an organism that eats other organisms • This trait sets animals apart from plants (there are only a few exceptions of plants that eat other organisms)
– Animals eat a great variety of foods– Examples: pandas eat bamboo
– Spiders eat other animals– Butterflies drink nectar from flowers