首页
登录
职称英语
"Symbiotic Relationships" Symbiosis is a close, long-lasti
"Symbiotic Relationships" Symbiosis is a close, long-lasti
游客
2024-01-04
30
管理
问题
"Symbiotic Relationships"
Symbiosis is a close, long-lasting physical relationship between two different species. In other words, the two species are usually in physical contact and at least one of them derives some sort of benefit from this contact. There are three different categories of symbiotic relationships: parasitism, commensalism, and mutualism.
Parasitism is a relationship in which one organism, known as the parasite, lives in or on another organism, known as the host, from which it derives nourishment. Generally, the parasite is much smaller than the host. Although the host is harmed by the interaction, it is generally not killed immediately by the parasite, and some host individuals may live a long time and be relatively little affected by their parasites. Some parasites are much more destructive than others, however.
Newly established parasite/host relationships are likely to be more destructive than those that have a long evolutionary history.
With a longstanding interaction between the parasite and the host, the two species generally evolve in such a way that they can accommodate one another. It is not in the parasite’s best interest to kill its host. If it does, it must find another. Likewise, the host evolves defenses against the parasite, often reducing the harm done by the parasite to a level the host can
tolerate
.
→ Parasites that live on the surface of their hosts are known as
ectoparasites
. Fleas, lice, and some molds and mildews are examples of ectoparasites.A Many other parasites, like tapeworms, malaria parasites, many kinds of bacteria, and some fungi, are called
endoparasites
because they live inside the bodies of their hosts.B A tapeworm lives in the intestines of its host where it is able to resist being digested and makes use of the nutrients in the intestine. C
Even plants can be parasites. Mistletoe is a flowering plant that is parasitic on trees. It establishes itself on the surface of a tree when a bird transfers the seed to the tree. It then grows down into the water-conducting tissues of the tree and uses the water and minerals it obtains from these tissues to support its own growth. D
If the relationship between organisms is one in which one organism benefits while the other is not affected, it is called commensalism. It is possible to visualize a parasitic relationship evolving into a commensal one. Since parasites generally evolve to do as little harm to their host as possible and the host is combating the negative effects of the parasite, they might eventually evolve to the point where the host is not harmed at all. There are many examples of commensal relationships. Orchids often use trees as a surface upon which to grow. The tree is not harmed or helped, but the orchid needs a surface upon which to establish itself and also benefits by being close to the top of the tree, where it can get more sunlight and rain. Some mosses, ferns, and many vines also make use of the surfaces of trees in this way.
In the ocean, many sharks have a smaller fish known as a remora attached to them. Remoras have a
sucker
on the top of their heads that they can use to attach to the shark. In this way, they can hitchhike a ride as the shark swims along. When the shark feeds, the remora frees itself and obtains small bits of food that the shark misses. Then, the remora reattaches. The shark does not appear to be positively or negatively affected by remoras.
→ Mutualism is another kind of symbiotic relationship and is actually beneficial to both species involved. In many mutualistic relationships, the relationship is obligatory; the species cannot live without each other. In others, the species can exist separately but are more successful when they are involved in a mutualistic relationship. Some species of Acacia, a thorny tree, provide food in the form of sugar solutions in little structures on their stems. Certain species of ants feed on the solutions and live in the tree, which they will protect from other animals by attacking any animal that begins to feed on the tree. Both organisms benefit; the ants receive food and a place to live, and the tree is protected from animals that would use it as food.
→ One soil nutrient that is usually a limiting factor for plant growth is nitrogen. Many kinds of plants, such as beans, clover, and alder trees, have bacteria that live in their roots in little
nodules
. The roots form these nodules when they are infected with certain kinds of bacteria. The bacteria do not cause disease but provide the plants with nitrogen-containing molecules that the plants can use for growth. The nitrogen-fixing bacteria from the living site and nutrients that the plants provide, and the plants benefit from the nitrogen they receive.
Glossary
sucker: an adaptation for sucking nourishment or sticking to a surface
nodules: growths in the form of knots [br] The word relatively in the passage is closest in meaning to
选项
A、comparatively
B、routinely
C、adversely
D、frequently
答案
A
解析
In this passage, comparatively is a synonym for "relatively." Context comes from the phrase "not killed immediately" in the same sentence.
转载请注明原文地址:https://tihaiku.com/zcyy/3332747.html
相关试题推荐
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lasti
"SymbioticRelationships"Symbiosisisaclose,long-lastingphysicalrelatio
"SymbioticRelationships"Symbiosisisaclose,long-lastingphysicalrelatio
随机试题
Traditionally,universitieshavecarriedouttwomainactivities:researcha
Hemanagedtosave______hecouldtotendthehomelessboy.A、whatlittletimeB
下列不属于新闻选择的基本环节的是()。A.新闻采访 B.新闻线索 C.新闻
某机械厂锻造车间噪声很大,作业人员由于长时间接触高分贝噪声,导致听阈升高。为降低
减免税作为税收优惠政策的核心内容,体现了税法的统一性与灵活性的有机结合。下列关于
由于工期紧,客户要求检测机构缩短规范标准规定样品养生时间或样品静置时间完成检测项
胰头癌最常见的首发症状是A.上腹痛和上腹饱胀不适 B.黄疸 C.消化道症状
《变电评价管理规定》要求,年度状态评价执行班组、()、评价中心三级评价机制。
施工总包单位应对其分包的建设工程质量承担()。A.总包责任 B.连带责任
投资项目决策分析与评价的基本要求包括贯彻落实科学发展观、资料数据准确可靠和()
最新回复
(
0
)