Category Environtal Studies

For most grazing animals, being part of a herd is their best defence against attack. Although individual animals, especially young, old or sick ones, may be picked off by predators, most animals will be safe. There are also more animals to watch out for danger while the rest graze. When attacked, the best defence of an antelope or zebra is its speed. At least over short distances, it can usually outrun its attackers. Wildebeest and some other heavier animals also have a powerful kick, which can break the bones of a lion or hyena if well aimed.

Defense mechanisms are very important to all animal life. Animals in every biome must eat to survive. With predators being high on the food chain and always on the lookout for a meal, prey must constantly avoid being eaten. Adaptations that prey employ ads to the chances of survival for the species. Some of these adaptations include defense mechanisms that can give prey an advantage against their enemies.

There are several ways animals avoid falling prey to a predator. One way is very direct and comes naturally. Imagine you are a rabbit and you have just noticed a fox preparing to attack. What would be your initial response? Right, you’d run. Animals can use speed as a very effective means of escaping predators. Remember, you can’t eat what you can’t catch!

Another defense mechanism is camouflage or protective coloration. One form, cryptic coloration, allows the animal to blend in with its environment and to mask its identity. Cryptic coloration is important to the survival of many new-born and young animals, as it is often their main defense against being detected by predators. Some animals blend in so well with their environment that it is very difficult to identify them. For example, some insects and other animals can look like leaves; both in their visual appearance and their behavior. It is important to note that predators also use cryptic coloration to avoid detection by unsuspecting prey.

When faced with danger, some animals pretend to be dead. This type of adaption is known as thanatosis. Opossums and snakes can even emit a fluid that produces a foul smell, thus adding to the pretense. Such behavior tricks predators into thinking that the animal is dead. Since most predators avoid dead or rotting animals, this type of defense mechanism is often very effective.

Some animals try to avoid predators by simply running, flying or swimming away as fast as they can. This is a very common defense mechanism that many animals use. Many animals that use speed as a defense live in open habitats, which don’t provide many places to hide from predators. Many animals that rely on speed also have excellent vision or hearing, so they can detect predators before they get very close.

To sum it all up, the predator-prey relationship is important to maintaining balance among different animal species. Adaptations that are beneficial to prey, such as physical defenses, ensure that the species will survive. At the same time, predators must undergo certain adaptive changes to make finding and capturing prey less difficult.

Without predators, certain species of prey would drive other species to extinction through competition. Without prey, there would be no predators. The animal organisms in such an environment could become endangered or even extinct. The predator-prey relationship ensures that the cycle of nutrients in biomes continues. Thus, this relationship is vital to the existence of life as we know it.

Grasses are well suited to being grazed. Although many will grow to more than two metres (over six feet) if left undisturbed, they do not need to reach this height to reproduce. Even if a flower and seed head are never allowed to form, the plant can reproduce by sending out runner’s underground, from which new daughter plants can grow. As well as being able to grow upwards from their central stem, grasses also have lower growing points from which new stalks can grow if the central one is cut. In fact, by this means grasses grow more thickly than ever, giving more food for grazing animals to eat.

Grasses are amazing, living beings that most of us don’t really consider of importance. Grasses have evolved with grazing animals so that they can thrive after being eaten by grazing animals. Grasses don’t survive grazing: they thrive with grazing. How do they do it? These reasons are why grasses are particularly awesome, in my book, and how they “survive” with not just grazing, but fire too:

1. The main growth point is at the very base of the plant, close to the soil surface that doesn’t get eaten by most animals.
2. Other growth points are at the base of each leaf. A leaf that hasn’t quite reached maturity and is clipped off by a lawn-mower blade or grazing animal will continue to grow. Leaves that have reached maturity die from the tip down. Leaves get continually replaced by tillers at the base.
3. They have daughter tillers at the base of every parent plant that grow up to replace the senesced or dead parent plants.
4. Some grass species form ever-growing bunches. Some bunch grasses, like rough fescue, can have hundreds of tillers in one plant. Others spread out via rhizomes forming a dense sod.
5. Grasses are particularly aggressive and determined to set seed before being defoliated again to spread out as much of their species as possible
6. Some species are very picky about when to set seed; particular climate conditions and stressors will prompt some plants to set seed, while other conditions encourage them to wait for the right time
7. Many native grasses are “decreases” under continued grazing (and with no grazing to control them eventually dominate the landscape), while other grasses are quite masochistic and love being grazed (the “increasers”) because it encourages them grow and spread out more.
8. The roots of grasses are very fibrous and can grow to depths of 10 feet or more; the native prairie grasses of the tall-grass prairie are particularly famous for such massive root systems.

Roots are a good indicator of how healthy grasses are, and not all species have deep roots. Lawn grasses and many forage grasses have shallow root systems. But, root systems become increasingly shallow with continual heavy grazing, unlike those grasses that either doesn’t get grazed at all, or less frequently.

Grasses need predators, though, in order for them to truly thrive and survive. Without predators like wolves, lions, or even humans, grasses can suffer from overgrazing by even the “native” grazers. Predators force grazing animals to move on to fresh grounds, and in doing so allow grasses to rest and recover sufficiently for the next bout of grazing animals to come through.

Grasses can be killed with excessive grazing and trampling. There’s no doubt about that. Simply leave a herd of grazing animals in one small area for a long period of time—and it doesn’t matter what species they are—and you’ll eventually find bare patches of earth showing through. If you remove these animals from that area for a long period of time, those patches disappear and grasses recover to produce a lot of herbage for those animals to consume.

The climates of the world’s grasslands vary a great deal. In Africa there are huge areas of grassland called savannah. These are warm all year round with summer rains. They support large populations of seed-eating birds and grazing animals, which in turn provide food for large meat-eating animals, such as lions, leopards, cheetahs, hyenas and jackals. The North American prairies and Russian steppes are similar in having hot summers but very cold winters. Great herds of bison once roamed the North American “sea of grass”, but early settlers killed enormous numbers of them for food and sport. Now the bison is a protected species. South American grasslands, called pampas, and the South African veld have sparser tussocks of grass.

Found in the middle of large land masses or continents. The two major areas are the prairies in North America and the steppe which straddles Europe and Asia. The majority of this biome is found between 40° and 60° north or south of the Equator.

There is a large temperature range between this region’s cold winters and hot summers, as this region is far from the moderating effect of sea breezes (warming in winter, cooling in summer) because they are found inland. A great variety of temperatures may also occur in the same place within a single day. Temperatures may change by as much as 30 °C from day to night, a diurnal (geographer’s word for daily) difference only beaten by hot deserts. However with total rainfall of between 250-500mm per year, this is a much wetter biome than a desert.

Temperate grasslands are known as the Prairies in North America, Pampas in Argentina and in Europe and Asia this kind of ecosystem is called Steppe. In New Zealand this zone includes the Canterbury Plains, and in South Africa it’s part of the Veld.

This biome is of real importance to humans for food production. Their dark, deep soils are amongst the richest in the world. This feature of temperate grasslands means that a lot of this biome is in fact now farm land. For example less than one per cent of the Prairies remain untouched, surrounded by gigantic flat fields of maize and wheat or cattle ranches.

Plants that flourish here are primarily grasses like grama and buffalo grass. It is too dry for trees here. Some grasses grow up to two metres in height in patchy tufts, whereas other feather-like plants carpet a vast area but only grow to a maximum of 50cm. The deep roots of these grasses seek out underground stores of water up to two metres below the ground. In temperate grasslands rainfall is limited apart from in late spring and early summer when seeds wake up and grow quickly, using nutrients released as last year’s plant growth rots down. The new grass provides food for grazing animals like bison, deer, and if you’re in Australia, Kangaroos. The rhea is a big flightless bird that makes its home in South America. They too eat leaves and seeds but also love lizards and beetles. Animals that like meat and veg like Rhea are called omnivores.

Wild animals remain in abundance where temperate grassland has been conserved. In the Prairies grasshoppers feed on grass but themselves make a tasty meal for prairie dogs. Prairie dogs in turn need to keep a look out for predators like rattlesnakes, coyotes and golden eagles. These ground-living squirrels live in colonies or groups and make their homes deep underground. The heaps of soil left by their burrowing form handy look out humps. Underground living can have its advantages in a place where the temperature can vary greatly, from 40 °C in summer (phew) to -40 °C in winter. The temperature also changes a lot within a twenty-four hour period in this kind of ecosystem. In Mongolia temperatures might rise and fall by as much as thirty degrees centigrade!

When not shaded by larger plants, grasses grow very quickly, especially if frequently nibbled or cut, as anyone who has to help mow a lawn knows. Up to 30% (almost a third) of the Earth’s land is covered by grassland. Grass plants can survive fire, which spreads rapidly across the land but burns for only a short time, as there is little to fuel it. Flash floods are also not a problem, as the shallow, dense roots of the grasses prevent the soil from being washed away.

The global importance of grasslands is indicated by their extent; they comprise some 26% of total land area and 80% of agriculturally productive land. The majority of grasslands are located in tropical developing countries where they are particularly important to the livelihoods of some one billion poor peoples. Grasslands clearly provide the feed base for grazing livestock and thus numerous high-quality foods, but such livestock also provide products such as fertilizer, transport, traction, fibre and leather. In addition, grasslands provide important services and roles including as water catchments, biodiversity reserves, for cultural and recreational needs, and potentially a carbon sink to alleviate greenhouse gas emissions. Inevitably, such functions may conflict with management for production of livestock products. Much of the increasing global demand for meat and milk, particularly from developing countries, will have to be supplied from grassland ecosystems, and this will provide difficult challenges. Increased production of meat and milk generally requires increased intake of metabolizable energy, and thus increased voluntary intake and/or digestibility of diets selected by grazing animals. These will require more widespread and effective application of improved management. Strategies to improve productivity include fertilizer application, grazing management, greater use of crop by-products, legumes and supplements and manipulation of stocking rate and herbage allowance. However, it is often difficult to predict the efficiency and cost-effectiveness of such strategies, particularly in tropical developing country production systems. Evaluation and on-going adjustment of grazing systems require appropriate and reliable assessment criteria, but these are often lacking. A number of emerging technologies may contribute to timely low-cost acquisition of quantitative information to better understand the soil-pasture-animal interactions and animal management in grassland systems. Development of remote imaging of vegetation, global positioning technology, improved diet markers, near IR spectroscopy and modeling provide improved tools for knowledge-based decisions on the productivity constraints of grazing animals. Individual electronic identification of animals offers opportunities for precision management on an individual animal basis for improved productivity. Improved outcomes in the form of livestock products, services and/or other outcomes from grasslands should be possible, but clearly a diversity of solutions are needed for the vast range of environments and social circumstances of global grasslands.

By domesticating goats, cattle, sheep, pigs and poultry, humans have been able to ensure that food is always available. Horses, mules and camels have been used to carry people and goods over long distances. Pets provide companionship but can also be very useful. Sheepdogs help farmers to round up their flocks. Guide dogs for the blind and hearing dogs for the deaf help their owners to lead full lives. Animals are also used to guard property, perform rescues and carry messages.

The specific economic application of domesticated animals did not appear at once. Dogs probably accompanied hunters and helped them hunt wild animals; they probably also guarded human settlements and warned the inhabitants of possible danger. At the same time, they were eaten by humans, which was probably their main importance during the first stages of domestication. Sheep and goats were also eaten in the initial stages of domestication but later became valuable for producing the commodities of milk and wool.

The principal aim of cattle breeding in ancient times was to obtain meat and skin and to produce work animals, which greatly contributed to the development of agriculture. Cattle, at the initial stages of domestication, produced a small amount of milk, sufficient only to rear their calves. The development of high milk yield in cows with their breeding especially for milk production is a later event in the history of domestication.

The first domesticated horses were also used for meat and skin. Later the horse played an enormous role in the waging of war. Peoples inhabiting the Middle East in the 2nd millennium BCE used horses in chariot battles. With time the horse began to be used as transportation. In the 1st millennium BCE carts appeared, and the horses were harnessed to them; other riding equipment, including the saddle and the bit, seems to have appeared in later centuries.

The donkey and the camel were used only for load transport and as means of conveyance; their unpalatability ruled out their use as a preferred food.

The first domesticated hens perhaps were used for sport. Cockfighting was instrumental in bringing about the selection of these birds for larger size. Cocks later acquired religious significance. In Zoroastrianism the cock was associated with protection of good against evil and was a symbol of light. In ancient Greece it was also an object of sacrifice to gods. It is probable that egg production of the first domesticated hens was no more than five to ten eggs a year; high egg yield and improved meat qualities of hens developed at later stages of domestication.

Early domestication of the cat was probably the result of the pleasure experienced from keeping this animal. The cat’s ability to catch mice and rats was surely another reason that impelled people to keep cats at home. In ancient Egypt the cat was considered a sacred animal.

Some animals were domesticated for utilitarian purposes from the very beginning. Here belongs, first of all, the rabbit, whose real domestication was carried out from the 6th to the 10th century CE by French monks. The monks considered newborn rabbits “fish” and ate them when the church calendar indicated abstinence from meat.

For the sake of honey, the bee was domesticated at the end of the Neolithic Period. Honey has played an enormous role in human nutrition since ancient times; it ceased being the sole sweetening agent only about 200 years ago. Bees also provided wax and bee venom, which was used as medicine. Bees were used also, to a limited extent, in warfare, hives being thrown among enemy troops to rout them.

To obtain silk, the silkworm was domesticated in China no later than 3000 BCE, and by 1000 BCE the technology of silkworm breeding and raising had been thoroughly documented.

Shepherd and nomadic animal breeding, which determined the social and economic organization and the way of life of some peoples to a great extent, appeared at later stages of human development, after the accumulation of a large number of domestic animals. Rudiments of nomadic animal breeding in Eurasia appeared no earlier than 1000 BCE, considerably after the domestication of animals took place.

The process of domestication in the New World took place somewhat later than in the Old World and independently of the latter, since humans first appeared in the New World only during the end of the Pleistocene Epoch (which lasted from 2.6 million to 11,700 years ago), long after settlement of the Old World.

Even the tiniest living things may be parasites. The micro-organisms that cause malaria and sleeping sickness, for example, are parasites that need more than one host to complete their life cycles. The diseases are spread by infected insects, which bite human beings to feed on their blood and in so doing pass on the infection. The organisms multiply in the person’s body, causing illness. The cycle is completed when an infection-free insect bites the person and in its turn becomes a carrier of the disease.

Cross-species transmission (CST), also called interspecies transmission, host jump, or spillover, is the ability for a foreign virus, once introduced into an individual of a new host species, to infect that individual and spread throughout a new host population. Steps involved in the transfer of viruses to new hosts include contact between the virus and the host, infection of an initial individual leading to amplification and an outbreak, and the generation within the original or new host of viral variants that have the ability to spread efficiently between individuals in populations of the new host Often seen in emerging viruses where one species transfers to another, which in turn transfers to humans. Examples include covid-19, HIV-IDS, SARS, Ebola, swine, rabies, and avian influenza. Bacterial pathogens can also be associated with CST.

The exact mechanism that facilitates transfer is unknown; however, it is believed that viruses with a rapid mutation rate are able to overcome host-specific immunological defenses. This can occur between species that have high contact rates. It can also occur between species with low contact rates but usually through an intermediary species. Bats, for example, are mammals and can directly transfer rabies to humans through bite and also through aerosolization of bat saliva and urine which are then absorbed by human mucous membranes in the nose, mouth and eyes. Note: the document used as a reference does not use the words urine or saliva so this citation is questionable. A host shifting event is defined as a strain that was previously zoonotic and now circulates exclusively among humans.

Similarity between species, for example, transfer between mammals, is believed to be facilitated by similar immunological defenses. Other factors include geographic area, interspecies behaviours, and phylogenetic relatedness. Virus emergence relies on two factors: initial infection and sustained transmission.

A parasite is a living thing that benefits from a relationship with another species but actually causes harm to that species. Some fungi are found on dying birch trees and can also live for a while on the wood after the tree has died.