What kind of animal can do this?

When I was moving to another house, I found this plastic bag on the top of the cabinet of my old house. It looks like someone cut it all with a scissor, but no one have access to my bedroom, and it was not me.

I don't thing it could be rats. That bedroom was very tiny and closed, there's no way for a rat to enter.

The house is very near a university with a little "forest", there are many types of mosquito and little flying animals, but I can't imagine which could do this.

I'm just curious. (and not sure if "zoology" is the correct tag here, but I had to choose one)

Although your plastic bag tears are most likely due to light damage as @Chris mentioned above, there is a type of ant that chews its way through plastic, rubber and other manufactured polymers: Monomorium pharaonis, the Pharaoh ant.

It is capable of destroying many manufactured materials and is a great example of budding, a method by which new ant colonies form. They are very invasive and difficult to control.

Is sex always determined by genetics and fixed from birth in animals? It’s an interesting question with perhaps a surprising answer – No! On this page, we explore animals whose sex changes with environmental conditions during development and animals that change sex throughout their lifetime. Read more.

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What Can I Do With an Animal Science Major?

Students can live at one of nine animal facilities at UC Davis. In exchange for about 10 hours of animal care per week, they receive free rent for a year, with a potential second year of residency.

These facilities include the:

Applications, found at the Animal Science Advising Center, are due in mid-March.

Let me introduce myself. I am Kathryn Jackson, student academic advisor in the Department of Animal Science. I am also a UC Davis alumna.

Many students enter the animal science major with the intention of applying to schools of veterinary medicine. But this popular major is also appropriate for other professional careers such as becoming a doctor, nurse, dentist or physician assistant. Continuing on to graduate school to earn a master’s degree or Ph.D. to become a researcher, scientist or professor after graduation is another option. This popular major is also appropriate for pre-health students on a medical, nursing, dental or physician’s assistant track.

Let me give you more examples.

Animal science careers with a bachelor’s degree

Our students have become zookeepers biologists butchers and animal production managers in dairies, beef ranches, horse farms, poultry houses and fish farms.

Working at UC Davis is also a possibility: Several of our recent graduates have been appointed staff positions at our department’s animal facilities.

We also have alumni who have gone on to work in animal shelters as adoption counselors and animal health technicians. One is a dog handler for the Transportation Security Administration.

Graduate degrees to become a researcher or professor

Another option for our majors is to continue on to graduate school for a master’s degree or Ph.D. to become a researcher, scientist or professor.

Researching human medicine with animal models is another popular and lucrative career. Local biotechnology firms such as Genentech and Jackson Laboratories actively recruit our students.

Animal science majors also have entered the agriculture regulation and policy sectors, choosing such careers as working for the USDA in carcass inspection or food safety.

And some graduates also have careers formulating pet and livestock feeds, working in a human eye research laboratory and teaching animal science at a community college.

Students exposed to many different species

As students move through the major, they are exposed to many different species including pets, livestock, horses, birds and fish. They get a broad education on how animals are used by people, and upper-division coursework focuses more on anatomy and physiology, genetics, nutrition, and behavior.

Students are required to select a focus area and complete courses in an area of specialization such as horses, companion animals or livestock, or a subject area such as physiology or behavior.

Many of our courses include laboratory components with live animals, dissections, surgeries or field trips to animal production facilities. These experiences often influence career paths as students learn what species and activities they enjoy most.

Intern at the zoo, vet hospital or water buffalo dairy

Our internship opportunities are broad and diverse. Students can intern at the Veterinary Medicine Teaching Hospital, the Sacramento Zoo and even a water buffalo dairy! Although internships are not required as part of the major, these hands-on experiences can be life-changing as students are involved in real-life learning with animal industry leaders.

Career development is an important activity in our Animal Science Advising Center. We communicate often with our students through Facebook, our website, e-mail and flyers. Continuing students can learn about part-time jobs.

Check out our Department of Animal Science website for links to career positions for newly graduated students, including jobs at UC Davis. The site may also be helpful to students exploring what they could do with an animal science degree. Also, join us on our Facebook page.

Get connected through our career symposium

Each winter our advising center hosts a half-day Saturday event called the Animal Science Career Symposium. We invite our alumni to come and speak to students to demonstrate what helped these professionals decide on a career path as they went through our major. They also help our continuing students identify what employers look for in potential employees.

We also invite recruiters from organizations such as the USDA, California Fish and Wildlife, the SPCA and Foster Farms to come meet and collect resumes from students at the end of the event.

This highly successful meeting has helped our students become better prepared for employment in animal-related fields as well as provided alumni with the opportunity to give back to the department through their time and valuable advice.

You will be spending 30 or more years in the career of your choice. If you are passionate about animals and science, the animal science major may be the perfect choice for you!

What types of animal enrichment are there?

Ideally, animals are given multiple types of enrichment, and the form of enrichment is changed periodically to continue giving them new stimulation. Though they are not mutually exclusive, enrichment can be broken up into five different categories:

Social enrichment is anything that includes social interactions, often with other live animals. It can include living with conspecifics, which means more of the same species, or other species of animals that can live together peacefully. It could also include people, or even stuffed animals and mirrors to simulate company, or a rival.

Cognitive enrichment is anything new or challenging that will make the animal think, be challenged, or become curious. For example, puzzle feeders, where they must solve a puzzle to obtain their food, brand new food they have never tried, new smells, or even training sessions.

Enrichment of physical habitat is exactly how it sounds: something is added to make their habitat more dynamic, comfortable, and/or fun. Perches for flying and climbing animals, places to hide for insects or prey animals, new dirt for digging or rolling in, etc., are all part of this category.

Sensory enrichment is anything that stimulates an animal’s senses, such as scratch boards, new smells, moving toys, or different sounds.

Food enrichment involves either new food items, or different ways for the animals to get their food. Food can be presented in a way that encourages foraging behavior, which is the way in which an animal searches for and obtains its food, such as scattering food, putting it inside an item that must be broken open, or maybe even burying it.

Different types of behavior evolved in animals because the behaviors helped them survive or reproduce. In many species, animals live together in a close-knit group with other members of their species. Such a group is referred to as a society. Animals that live in a society are known as social animals. They live and work together for the good of the group. This is called cooperation. Generally, each member of the group has a specific role that it plays in the society. Cooperation allows the group to do many things that a lone animal could never do. Look at the ants in Figure below. By working together, they are able to carry a large insect back to the nest to feed other members of their society.

Cooperation in a Social Insect. These ants are cooperating in a task that a single ant would be too small to do alone.


For individuals to cooperate, they need to communicate. Animals can communicate with sounds, chemicals, or visual cues. For example, to communicate with sounds, birds sing and frogs croak. Both may be communicating that they are good mates. Ants communicate with chemicals called pheromones. For example, they use the chemicals to mark trails to food sources so other ants can find them. Male dogs use pheromones in urine to mark their territory. They are &ldquotelling&rdquo other dogs to stay out of their yard. You can see several examples of visual communication in Figure below.

Visual Communication in Animals. Many animals use visual cues to communicate.


Aggression is behavior that is intended to cause harm or pain. It may involve physical violence against other individuals. For example, two male gorillas may fight and use their canine teeth to inflict deep wounds. Expressing aggression this way may lead to serious injury and even death.

In many species display behaviors, rather than actual physical attacks, are used to show aggression. This helps prevent injury and death. Male gorillas, for example, are more likely to put on a display of aggression than to attack another male. In fact, gorillas have a whole series of display behaviors that they use to show aggression. They beat on their chest, dash back and forth, and pound the ground with their hands.


Aggressive behavior often occurs when individuals compete for the same resources. Animals may compete for territory, water, food, or mates. There are two basic types of competition: intraspecific and interspecific.

  • Intraspecific competition occurs between members of the same species. For example, two male deer may compete for mates by clashing their antlers together.
  • Interspecific competition occurs between members of different species. For example, one species of ant may attack and take over the colony of another ant species.

Find more animals like this

Quick Facts

  • Type: Mammal
  • Diet: Herbivore
  • Life span: 5-10 years
  • Size: 90-140 cm
  • Weight: 40-130 kg
  • Habitat: Grass plains and mountains
  • Range: Originated from Europe and Asia, domesticated breeds now common in the Americas and Australasia
  • Scientific name: Ovis Aries

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Insect Anti-Freeze

Picture holding an insect in your hand and how tiny it looks compared to you and everything else. Even small insects live in the tundra. But how do they survive in below-freezing temperatures? For some, the answer is antifreeze.

If you’ve heard of antifreeze, it was probably from someone with a car. In cars, antifreeze is a manmade (and very dangerous) chemical mixture that allows all the water-based liquids to operate in a wide range of low and high temperatures.

All the tiny dots in this picture are mosquitoes. But how do mosquitoes live in the cold conditions of the tundra? Click for more detail.

Just like it’s important for a car to function, antifreeze in tundra insects is critical for life. Insect antifreeze is a naturally occurring protein that lowers the freezing point of water in insect bodies.

The protein's structure also lets it attach to ice crystals to prevent more from forming. Not only do insects benefit from this adaptation, but arctic fish do as well.

The cold can affect insects in other ways, as some insects mature very slowly, perhaps taking 10 to 15 years to pass through all their larval stages. This slow growth occurs because they can only get a little food each short summer. No matter the size of the animal, life in the tundra can be tough.

Animal Characterization Based on Features of Embryological Development

Most animal species undergo a separation of tissues into germ layers during embryonic development. Recall that these germ layers are formed during gastrulation, and that they are predetermined to develop into the animal’s specialized tissues and organs. Animals develop either two or three embryonic germs layers (Figure 4). The animals that display radial symmetry develop two germ layers, an inner layer (endoderm) and an outer layer (ectoderm). These animals are called diploblasts. Diploblasts have a non-living layer between the endoderm and ectoderm. More complex animals (those with bilateral symmetry) develop three tissue layers: an inner layer (endoderm), an outer layer (ectoderm), and a middle layer (mesoderm). Animals with three tissue layers are called triploblasts.

Art Connection

Figure 4. During embryogenesis, diploblasts develop two embryonic germ layers: an ectoderm and an endoderm. Triploblasts develop a third layer—the mesoderm—between the endoderm and ectoderm.

Which of the following statements about diploblasts and triploblasts is false?

  1. Animals that display radial symmetry are diploblasts.
  2. Animals that display bilateral symmetry are triploblasts.
  3. The endoderm gives rise to the lining of the digestive tract and the respiratory tract.
  4. The mesoderm gives rise to the central nervous system.

Each of the three germ layers is programmed to give rise to particular body tissues and organs. The endoderm gives rise to the lining of the digestive tract (including the stomach, intestines, liver, and pancreas), as well as to the lining of the trachea, bronchi, and lungs of the respiratory tract, along with a few other structures. The ectoderm develops into the outer epithelial covering of the body surface, the central nervous system, and a few other structures. The mesoderm is the third germ layer it forms between the endoderm and ectoderm in triploblasts. This germ layer gives rise to all muscle tissues (including the cardiac tissues and muscles of the intestines), connective tissues such as the skeleton and blood cells, and most other visceral organs such as the kidneys and the spleen.

Presence or Absence of a Coelom

Further subdivision of animals with three germ layers (triploblasts) results in the separation of animals that may develop an internal body cavity derived from mesoderm, called a coelom, and those that do not. This epithelial cell-lined coelomic cavity represents a space, usually filled with fluid, which lies between the visceral organs and the body wall. It houses many organs such as the digestive system, kidneys, reproductive organs, and heart, and contains the circulatory system. In some animals, such as mammals, the part of the coelom called the pleural cavity provides space for the lungs to expand during breathing. The evolution of the coelom is associated with many functional advantages. Primarily, the coelom provides cushioning and shock absorption for the major organ systems. Organs housed within the coelom can grow and move freely, which promotes optimal organ development and placement. The coelom also provides space for the diffusion of gases and nutrients, as well as body flexibility, promoting improved animal motility.

Triploblasts that do not develop a coelom are called acoelomates, and their mesoderm region is completely filled with tissue, although they do still have a gut cavity. Examples of acoelomates include animals in the phylum Platyhelminthes, also known as flatworms. Animals with a true coelom are called eucoelomates (or coelomates) (Figure 5). A true coelom arises entirely within the mesoderm germ layer and is lined by an epithelial membrane. This membrane also lines the organs within the coelom, connecting and holding them in position while allowing them some free motion. Annelids, mollusks, arthropods, echinoderms, and chordates are all eucoelomates. A third group of triploblasts has a slightly different coelom derived partly from mesoderm and partly from endoderm, which is found between the two layers. Although still functional, these are considered false coeloms, and those animals are called pseudocoelomates. The phylum Nematoda (roundworms) is an example of a pseudocoelomate. True coelomates can be further characterized based on certain features of their early embryological development.

Figure 5. Triploblasts may be (a) acoelomates, (b) eucoelomates, or (c) pseudocoelomates. Acoelomates have no body cavity. Eucoelomates have a body cavity within the mesoderm, called a coelom, which is lined with mesoderm. Pseudocoelomates also have a body cavity, but it is sandwiched between the endoderm and mesoderm. (credit a: modification of work by Jan Derk credit b: modification of work by NOAA credit c: modification of work by USDA, ARS)

Embryonic Development of the Mouth

Figure 6. Eucoelomates can be divided into two groups based on their early embryonic development. In protostomes, part of the mesoderm separates to form the coelom in a process called schizocoely. In deuterostomes, the mesoderm pinches off to form the coelom in a process called enterocoely. It was long believed that the blastopore developed into the mouth in protostomes and into the anus in deuterostomes, but recent evidence challenges this belief.

Bilaterally symmetrical, tribloblastic eucoelomates can be further divided into two groups based on differences in their early embryonic development. Protostomes include arthropods, mollusks, and annelids. Deuterostomes include more complex animals such as chordates but also some simple animals such as echinoderms. These two groups are separated based on which opening of the digestive cavity develops first: mouth or anus. The word protostome comes from the Greek word meaning “mouth first,” and deuterostome originates from the word meaning “mouth second” (in this case, the anus develops first). The mouth or anus develops from a structure called the blastopore (Figure 6). The blastopore is the indentation formed during the initial stages of gastrulation. In later stages, a second opening forms, and these two openings will eventually give rise to the mouth and anus (Figure 6). It has long been believed that the blastopore develops into the mouth of protostomes, with the second opening developing into the anus the opposite is true for deuterostomes. Recent evidence has challenged this view of the development of the blastopore of protostomes, however, and the theory remains under debate.

Another distinction between protostomes and deuterostomes is the method of coelom formation, beginning from the gastrula stage. The coelom of most protostomes is formed through a process called schizocoely, meaning that during development, a solid mass of the mesoderm splits apart and forms the hollow opening of the coelom. Deuterostomes differ in that their coelom forms through a process called enterocoely. Here, the mesoderm develops as pouches that are pinched off from the endoderm tissue. These pouches eventually fuse to form the mesoderm, which then gives rise to the coelom.

The earliest distinction between protostomes and deuterostomes is the type of cleavage undergone by the zygote. Protostomes undergo spiral cleavage, meaning that the cells of one pole of the embryo are rotated, and thus misaligned, with respect to the cells of the opposite pole. This is due to the oblique angle of the cleavage. Deuterostomes undergo radial cleavage, where the cleavage axes are either parallel or perpendicular to the polar axis, resulting in the alignment of the cells between the two poles.

There is a second distinction between the types of cleavage in protostomes and deuterostomes. In addition to spiral cleavage, protostomes also undergo determinate cleavage. This means that even at this early stage, the developmental fate of each embryonic cell is already determined. A cell does not have the ability to develop into any cell type. In contrast, deuterostomes undergo indeterminate cleavage, in which cells are not yet pre-determined at this early stage to develop into specific cell types. These cells are referred to as undifferentiated cells. This characteristic of deuterostomes is reflected in the existence of familiar embryonic stem cells, which have the ability to develop into any cell type until their fate is programmed at a later developmental stage.

Evolution Connection

The Evolution of the Coelom

One of the first steps in the classification of animals is to examine the animal’s body. Studying the body parts tells us not only the roles of the organs in question but also how the species may have evolved. One such structure that is used in classification of animals is the coelom. A coelom is a body cavity that forms during early embryonic development. The coelom allows for compartmentalization of the body parts, so that different organ systems can evolve and nutrient transport is possible. Additionally, because the coelom is a fluid-filled cavity, it protects the organs from shock and compression. Simple animals, such as worms and jellyfish, do not have a coelom. All vertebrates have a coelom that helped them evolve complex organ systems.

Animals that do not have a coelom are called acoelomates. Flatworms and tapeworms are examples of acoelomates. They rely on passive diffusion for nutrient transport across their body. Additionally, the internal organs of acoelomates are not protected from crushing.

Animals that have a true coelom are called eucoelomates all vertebrates are eucoelomates. The coelom evolves from the mesoderm during embryogenesis. The abdominal cavity contains the stomach, liver, gall bladder, and other digestive organs. Another category of invertebrates animals based on body cavity is pseudocoelomates. These animals have a pseudo-cavity that is not completely lined by mesoderm. Examples include nematode parasites and small worms. These animals are thought to have evolved from coelomates and may have lost their ability to form a coelom through genetic mutations. Thus, this step in early embryogenesis—the formation of the coelom—has had a large evolutionary impact on the various species of the animal kingdom.

Seashell Formation

Seashells are typically formed in distinct layers via the extracellular secretion of proteins which are then covered by calcium carbonate. Therefore, the shell grows from the bottom upwards, with the constant secretion of new material at the margin between the animal and the shell. The tissue responsible for shell formation is called the mantle. The mantle resides at the interface between the body of the animal and the shell. As the animal grows, the shell also grows and becomes increasingly strong, to accommodate the larger size of the animal and provide adequate protection. There are three distinct layers of the shell produced by the mantle:

Outer proteinaceous periosteum

The outer proteinaceous periosteum is the non-calcified layer on the outer surface of the shell. It is composed of a thin, hard layer of dark protein which serves to protect the edge of the shell as it grows. This layer also provides the structural foundation on which the subsequent layers can be built and allows for the accumulation of calcium ions, which promotes crystallization.

Prismatic layer

The prismatic layer forms the middle layer of the shell, which is comprised of a hard, prismatic calcium carbonate which exhibits a chalky appearance. The prismatic and the periosteum layers are formed by the same specialized mantle cells.

Inner pearly layer (nacre)

The inner pearly layer is also calcified, but is a pearly lamellar substance which is formed by the epithelial cells of the mantle surface. Nacre is also referred to as “Mother of Pearl” and is known for its exceptional strength. Nacre is formed by the “brick-like” arrangement of calcium carbonate sheets interspersed with biopolymers which provides the shell with elasticity, strength, and resistance to cracking.

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