Name: why biodiversity matters in ecosystems
Uploaded: 2019-01-29T11:04:46.000Z
Duration: 5 min 41 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Earth and Environmental Science

Earth's Systems

ESS.EES.4.5

Measuring Biodiversity

生物多样性。这个词让人联想到广袤森林的壮丽，或海洋中生机勃勃的丰富生命，其简单定义即为特定生态系统中生物种类的多样性。为了保护生物多样性，科学家必须能够对其进行量化。这意味着需要弄清楚在特定空间内共同生活的不同物种数量。那么，有什么便捷的方法可以统计物种数量呢？

要统计整个生态系统中的所有生物是不可能的，因此科学家会使用一种称为样方的工具。样方是一个固定大小的框架，被随机放置在环境中用于进行计数。在记录了该小区域中发现的物种和个体之后，此过程会重复进行，将更多的样方随机放置，或者沿穿过环境的直线在设定的位置上放置，这种直线被称为样线。

为了估算某一区域内的物种总数，通常使用物种累积曲线。如果将每个样方中发现的累计物种数与所调查的样方数量作图，就会得到一条曲线。例如，在该数据集中，当调查了四个样方时，共发现10个不同的物种；六个样方时为17个，依此类推。此类曲线的渐近线代表该环境所能支持的物种数量的估计值。在本例中，该值约为30。尽管在单个地点测量多样性具有重要价值，但对更大范围内多个地点进行比较，能够为我们提供更宏观尺度上的多样性信息。

1972年，生态学家罗伯特·惠特克（Robert Whittaker）提出了生物多样性的三种主要类型：α多样性、β多样性和γ多样性。α多样性仅指某一区域内的物种数量，通常被称为物种丰富度。例如，该样地中有七个不同的物种，因此其α多样性值为7。第二个样地（样地B）有五个物种，第三个样地（样地C）有七个物种。但通过比较不同样地之间的物种组成，我们可以确定所谓的β多样性，即各个区域中特有物种的总和。因此，当我们比较样地A和样地B时，发现两者之间有三个共有物种。统计剩余的物种后，我们得到总数为六个。这意味着样地A与样地B之间的β多样性为6。样地A和样地C之间也有三个共有物种，剩下八个特有物种，其β多样性为8。样地B和样地C之间有两个共有物种，其β多样性值也为8。最后，γ多样性是指所有样地合并后的不同物种总数。在本例中，γ多样性为12。综上所述，这三种生物多样性可归纳如下：α多样性、β多样性和γ多样性。除了记录多样性外，科学家还常提到物种均匀度，即每种物种的个体数量分布情况。例如，这两个样地的物种丰富度（即α多样性）相同，均含有七个物种。但样地A中兔子数量占绝对优势，其他物种个体数较少，而样地B中各物种的分布较为均匀，因此其均匀度高于样地A。科学家通常认为，物种丰富度和均匀度较高的生态系统（即物种数量多且分布均匀）最为健康。受干扰的生境（通常由人类活动如农业或污染引起）往往表现出较低的丰富度和均匀度。能够对不同样地进行比较至关重要，因为它使研究人员得以评估生态系统的相对健康状况。 
在本实验中，你将在三个不同的生态环境样地开展样方和样线取样，并进行一次实验室模拟，随后分析所收集的数据，以描述所观察到的生物多样性。

测量生物多样性

多样的生态系统对于地球的健康以及人类的生存至关重要；因此，理解并测量生物多样性具有极其重要的意义。生物多样性被定义为生态系统中生物有机体之间的变异性，可在多个不同层次上进行测量，包括遗传、物种、群落和生态系统层次。测量生物多样性的一种方法是评估生态系统的物种丰富度，即一个局部群落中不同物种的总数。尽管物种数量多通常意味着生态系统具有较高的多样性和健康水平，但仍需考虑均匀度。均匀度指的是某一区域或群落中各个物种个体数量比例的均等程度。例如，当某一物种占据主导地位而其他物种极为稀少时，该区域的生物多样性低于物种个体数量相对均等的区域。因此，物种数量较多且各物种个体数量相对均衡的区域具有最高的生物多样性值。

<h4>生物多样性估算</h4>

两个群落之间在丰富度和均匀度上的差异可以通过等级-多度曲线进行可视化。如果物种数量相等，曲线的形状可以告诉我们哪个群落更具多样性。如果曲线较为平坦，说明物种间的均匀度较高；然而，如果曲线迅速下降，则表明均匀度较低。当两个群落的丰富度和均匀度均不同时，生物学家必须借助公式来计算多样性。这些公式对各个组分的重要性赋予不同的权重，目前科学界仍在争论哪种公式在计算多样性时最为理想。

有时一个区域内的物种数量过多，以至于不可能逐一清点所有物种。例如，亚马逊雨林中的一棵树上可能栖息着数百种不同的甲虫。为解决这一问题，生态学家会使用一种称为样方的取样工具。样方只是一个具有已知内部面积的框架。例如，为了测定一英亩草地的物种丰富度，生态学家会将样方随机放置在草地上，并统计样方内的物种数量，而不是清点整英亩土地上的所有物种。他们还可以采用样线带进行系统取样。样线带横跨整个样地拉伸，然后以固定间隔在线上放置样方。这种方法属于半随机取样，可确保对整个样地进行充分的取样覆盖，从而估算其生物多样性。

尽管样方和样线法可能记录到大多数物种，但一些稀有物种仍可能被忽略。此时，生态学家可能会使用物种累积曲线，该曲线表示在一系列样方中观察到的物种总数的累积情况。曲线的纵轴表示观察到的物种总数，横轴表示已统计物种数的样方数量。第一个样方中的物种总数即为曲线上第一个数据点。随后的每个数据点表示在每个新取样的样方中发现的新物种数，加上之前所有样方中的物种总数。在某一时刻，每个新取样的样方中发现的新物种将很少或没有，曲线将趋近于一个渐近线，该渐近线即为该区域物种总数的估计值。即使由于存在大量稀有物种而未能真正达到渐近线，生物学家仍可根据该曲线估算出物种总数。

若需对不同区域或尺度进行比较，则可采用α、β和γ多样性指标。α多样性（α）指某一区域内的物种数量。β多样性（β）用于比较两个不同区域，其值为各区域特有物种数的总和。γ多样性（γ）指多个区域合并为一个大区域后的总物种数。通过使用这些指标，生物学家能够了解从较小到较大空间尺度上的生物多样性分布情况。

<h4>生物多样性面临的威胁及其影响</h4>

全球的生物多样性正受到污染、气候变化和入侵物种的威胁。保护生物多样性的主要根本原因在于生态系统的功能。生态系统由许多组成部分构成，包括初级生产者、植食动物、肉食动物和食碎屑动物，它们均对生态系统功能有所贡献。如果物种丧失，生态系统可能会崩溃；而一旦生态系统崩溃，其为人类提供的各种生态服务也将随之消失。热带珊瑚礁就是这一概念的典型例证1。水温急剧升高会导致珊瑚失去其共生的藻类细胞。失去藻类后，珊瑚开始饥饿、死亡，继而退化并丧失其结构。当珊瑚腐烂后，便不再为鱼类提供庇护，鱼类物种的丰富度随之下降，进而影响当地渔民以及依赖鱼类作为食物来源的人群。随着时间推移，死亡的珊瑚礁在更大范围内退化，不再为邻近海岸提供缓冲作用，最终导致海岸侵蚀并摧毁岛屿。高度多样化的群落因功能冗余而较不易发生崩溃2。例如，不同珊瑚对高温的敏感性可能存在差异。如果一种珊瑚对温度极为敏感，另一种珊瑚可能在群落中取而代之；但如果物种数量稀少，则很难找到可替代的物种。

我们所受益的大量药物直接源于生命的多样性。如今我们能够合成的许多药物，最初都是从动物、植物、真菌和细菌中分离得到的。目前存在一个完整的产业，致力于通过筛查各种物种中是否存在生物活性化合物，来发现潜在的新药物。例如，植物会合成化学物质以防御感染和植食性动物；蜘蛛和蛇类则能产生多种多样的毒液。这两类生物都已为人类提供了重要的药物，比如从红豆杉中提取的用于治疗乳腺癌、肺癌和卵巢癌的紫杉醇（Taxol），以及从眼镜王蛇毒液中发现的镇痛剂Ohanin3-4。每一个灭绝的物种，都可能蕴藏着治愈目前无法治疗疾病的关键线索。物种消失的速度越快，我们发现这些解决方案的机会就越小。

一旦一个物种灭绝，我们将永远无法再体验到它们的存在。这种观念推动了对大熊猫、海獭以及其他具有魅力的动物的保护工作。这些物种被称为旗舰物种，对其保护有助于生物多样性的维护。尽管这些动物仅占整个生态系统的一小部分，但保护它们意味着保护其所栖息的整个生态系统。在北美西海岸开展的海獭保护工作，已促成了健康的巨藻森林的恢复，为成千上万的其他物种提供了栖息地5。若不保护海獭，其通常捕食的植食性生物（如海胆）将大量繁殖，完全吞噬巨藻森林，最终仅留下贫瘠的岩石，使极少数物种得以生存。

<h4>参考文献</h4>

<ol class="references">
	<li>Knowlton, Nancy. 珊瑚礁的未来。PNAS. 2001, Vol. 98 , (10) 5419-5425.</li>
	<li>Andrea S. Downing, Egbert H. van Nes, Wolf M. Mooij, Marten Scheffer. 生态系统对多样性崩溃的恢复力与抗性。PLoS One. . 2012; , Vol. 7(9): e46135.</li>
	<li>Wall, Monroe E. 喜树碱与紫杉醇：从发现到临床。Med Res Rev. 1998, Vol. 18, 5 (299-314)。</li>
	<li>Yuh Fen Pung, Peter T. H. Wong, Prakash P. Kumar, Wayne C. Hodgson, R. Manjunatha Kini. Ohanin：一种来自眼镜王蛇毒液的新型蛋白质，可诱导小鼠运动减少和痛觉过敏。J Biol Chem. 2005, 280, 13137-13147.</li>
	<li>Estes, J.A., 等. 海藻林生态系统中的复杂营养相互作用。Bulletin of Marine Science, Volume . 2004, Vol. 7, 3: 621-638.</li>
</ol>

多样的生态系统对于地球的健康以及人类的生存至关重要；因此，我们理解并……

Education

教育

JoVE Lab Manual

Biology

生物学

Ecology

生态学

衡量生物多样性

why biodiversity matters in ecosystems

Biodiversity matters because it helps keep ecosystems healthy and stable. Biodiversity is the variety of living organisms in an ecosystem, and it can be measured at the genetic, species, community, and ecosystem levels. Ecologists often focus on species richness, which is the total number of different species in a local community. They also consider evenness, which describes how similar the abundances of those species are.

A community with many species is not always the most diverse if one species dominates. When species are more evenly distributed, biodiversity is higher than in a community where rare species make up only a small part of the total. Biologists can compare communities with rank-abundance curves. A flat curve shows high evenness, while a curve that drops quickly shows low evenness. If richness and evenness both differ, ecologists use equations to calculate diversity, although there is still debate about which equation works best.

Counting every organism is often impossible. A single tree in the Amazon Rainforest may hold hundreds of beetle species. To estimate biodiversity, ecologists use quadrats, which are frames with a known area. They place quadrats randomly in a field or along transects, which are tapes stretched across an area so samples can be taken at regular intervals. This approach helps cover the site while making the survey practical.

Even with quadrats and transects, rare species can be missed. Ecologists use species accumulation curves to track the total number of species found as more quadrats are sampled. The curve rises as new species appear and eventually approaches an asymptote, which gives an estimate of the total number of species in the area. If the asymptote is not fully reached, scientists can still estimate how many species are likely present.

Biologists also compare diversity across space with alpha, beta, and gamma diversity. Alpha-diversity is the number of species in one area. Beta-diversity compares two areas and includes the species unique to each one. Gamma-diversity measures the number of species across many areas in a region. Together, these measures show diversity at small and large scales.

Biodiversity is threatened by pollution, climate change, and invasive species. Ecosystems depend on many working parts, including primary producers, herbivores, carnivores, and detritivores. If species are lost, the ecosystem can collapse, and the services it provides to people can disappear too. Coral reefs show this clearly. When water temperatures rise, corals lose their symbiotic algae cells, then starve, die, and lose their structure. Fish lose cover, fish numbers decline, fishermen are affected, and damaged reefs can no longer protect coastlines from erosion.

High biodiversity can make a community more resistant to collapse because of functional redundancy. If one coral species is very sensitive to heat, another may be able to fill its role. With only a few species, that backup is less likely. Biodiversity also supports medicine. Many medicines were first isolated from animals, plants, fungi, and bacteria. Scientists continue to search species for bioactive compounds, such as Taxol from yew trees for cancer treatment and Ohanin from king cobra venom as a painkiller. Each extinct species may remove a possible source of future cures.

Conservation often focuses on flagship species such as pandas and sea otters. Protecting these animals can also protect the ecosystems they live in. On the West Coast of North America, efforts to save sea otters helped keep kelp forests healthy and full of many other species. Without otters, sea urchins can overgraze kelp forests and leave barren rocks with very few species able to survive.

Why Biodiversity Matters in Ecosystems

animal behavior

Drosophila Taxis in Animal Behavior

Drosophila taxis behavior is a key part of animal behavior studies. The common fruit fly, Drosophila melanogaster, is a widely used model organism in biology. It is easy to keep in small tubes, it has a short generation time of about two weeks, and males and females are easy to tell apart because males have black coloration toward the posterior and females have banded abdomens. Scientists have used Drosophila for more than a century. Thomas Hunt Morgan and his students studied mutant flies in...

energy dynamics

Food Chain Energy Flow and Biomass

Food chain energy flow shows how energy moves through ecosystems from one organism to the next. Energy cannot be created or destroyed, so it can only change form or be passed along to another organism. When a cow grazes on grass or an osprey eats fish, energy moves to the consumer. Each transfer is part of a trophic level, and these links help explain how ecosystems stay balanced. Primary producers sit at the base of the food chain. They are autotrophs, or self-feeding organisms, because they...

measuring biodiversity

Biodiversity matters because it helps keep ecosystems healthy and stable. Biodiversity is the variety of living organisms in an ecosystem, and it can be measured at the genetic, species, community, and ecosystem levels. Ecologists often focus on species richness, which is the total number of different species in a local community. They also consider evenness, which describes how similar the abundances of those species are. A community with many species is not always the most diverse if one...

extinction

Mass Extinction and the Fossil Record

Mass extinction is a major loss of species, and the fossil record shows how these events changed life on Earth. Fossils from different rock layers helped scientists see that life has a long history. In the early 19th century, that idea helped launch paleontology, the study of fossils and ancient life. At first, many scientists did not fully accept that a species could disappear forever. They thought unknown organisms seen only in fossils might still live in unexplored places on Earth. By 1859,...

species distribution and biogeography

Island Biogeography and Species Richness

Island biogeography explains why species are found in some places and not others. It looks at how biotic factors, like competition and predation, and abiotic factors, like habitat size and distance, shape birth, death, immigration, and emigration rates. For a species to avoid local extinction, births and immigration must match or exceed deaths and emigration. Edward O. Wilson and Robert MacArthur helped define this field in 1967 by studying isolated oceanic islands. Islands gave early...

population growth

Population Models and Carrying Capacity

Population ecology examines how a species population changes over time. A population is a group of individuals of the same species living in the same area at the same time. To persist, a population must grow or at least stay about the same size. Ecologists study birth rate, death rate, and age distribution to understand whether a population is increasing, declining, or at risk of extinction. Population ecologists use models to predict how population size changes. Two simple models are...

community diversity

Measuring Ecosystem Health

Ecosystem health is measured by looking at how species, habitats, and nonliving conditions interact in the same area. An ecological community includes many populations that live together and affect one another. When biotic parts, or living parts, also interact with abiotic parts, or nonliving parts, they form an ecosystem. These systems can be very small, like microbes in the human digestive tract, or very large, like a forest linked by the carbon cycle. Ecologists study ecosystem health...

climate change

Climate Change Effects on Sea Level and Species

Climate change affects Earth’s average temperature, sea level, and living things. Scientists distinguish climate from weather by time scale. Weather describes short-term conditions in one place, such as temperature and precipitation. Climate describes those same conditions over long periods, and global climate is measured using data from across the entire Earth. Researchers track climate change with help from meteorology, geography, oceanography, and computer models. Much of this work focuses...

group behavior

Hawk-Dove Strategy in Animal Populations

Hawk-dove strategy helps explain how animals compete and cooperate in populations. Organisms often face costs when they try to get food, shelter, or mates. Because of that, individuals can use different behavioral strategies to gain an advantage. This is clear in polymorphic mating systems, where one sex, usually males, uses more than one mating strategy. For example, dominant male sea lions defend groups of females on the beach. Non-dominant males stay in or near the water and try to mate...

optimal foraging

Patch Use in Optimal Foraging

Patch use in optimal foraging explains how organisms balance food gain against the time and energy needed to search for it. Foraging is not limited to food. Animals also search for habitats, shelter, and mates. Each choice has costs and benefits. A resource provides a benefit, but finding and capturing it takes effort. Optimal Foraging Theory models how organisms reach the best balance between those costs and gains. A key idea in this theory is that resources are often clumped into patches...

sexual selection and mate choice

Mate Competition and Fitness Traits

Mate competition and fitness traits shape how organisms choose partners and pass genes to the next generation. Evolutionary fitness depends on surviving and producing offspring, and sexual selection is a major part of that process. It creates pressure on traits used in courtship and mating, such as bright colors, ornamentation, and other features that help attract a mate. These traits can also create sexual dimorphism, which means males and females of the same species look different. Sexual...

eusociality and division of labor

Honeybee Altruism and Inclusive Fitness

Eusociality is a highly organized form of animal social life. It includes division of labor, where different individuals take on different roles in the group. In these systems, some animals help others even when it comes at a cost to their own survival or reproduction. That self-sacrificing behavior is called altruism. Early evolutionary biologists used to explain fitness only at the level of the individual. Observations of eusocial species, such as honeybees, challenged that idea. W. D.

ecology

Learn how biodiversity is measured with richness, evenness, quadrats, and diversity curves, and why it protects ecosystems, medicine, and conservation.

Why Biodiversity Matters in Ecosystems | JoVE K12

Louisiana Student Standards for Science

High School

Earth Science

Human Sustainability

HS-ESS3-3

Life Sciences

ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy And Dynamics

HS-LS2-7

Environmental Science

Tennessee Academic Standards

Biological Change: Unity and Diversity

BIO1.LS4.3

Virginia  Standards of Learning

HIgh School

BIO.8

BIO.8.d

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Life Science

Ecosystems: Interactions, Energy, and Dynamics

HS-LS2-2

Arizona Science Standards

HS+B.L2

HS+B.L2U1.1

Alabama Course of Study Science

Ecosystems: Interactions Energy and Dynamics

9-12.B.2.9

Unity and Diversity

9-12.EVS.2.3.a

Next Generation Science Standards

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS4-6

Earth and Space Science

Earth’s Systems

HS-ESS2-6

Florida Department of Education

SC.912.L.15

SC.912.L.15.3

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

Biological Evolution: Unity and Diversity

B-LS4-6.

Georgia Standards of Excellence

SEV2.

SEV2.a

new-york-state-science-learning-standards

New York State Science Learning Standards

interdependent-relationships-in-ecosystems

Interdependent Relationships in Ecosystems

HS-LS2-2.

HS-LS2-7.

Earth and Space Sciences

HS-ESS2-7.

Entomology

SEN1.

SEN1.c

SEC5.

SEC5.c

SB5.a

通过这段 2 分钟的教师指南，准备教授 测量生物多样性。涵盖 JoVE Lab Manual 上 Biology 实验的关键准备步骤。

Biology 中的 测量生物多样性 教师准备 - 3.6K+ 观看次数 | JoVE Lab Manual

在这段 8 分钟的学生实验流程视频中，逐步学习 测量生物多样性 的操作步骤。属于 JoVE Lab Manual 上的 Biology 系列。

Biology 中的 测量生物多样性 学生实验流程 - 6.3K+ 观看次数 | JoVE Lab Manual

Igneous Volcanic Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
Igneous rocks are the products of cooling and crystallization of magma. Volcanic rocks ...

The Carbon Cycle

Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among ...

Igneous Intrusive Rock

Source: Laboratory of Alan Lester - University of Colorado Boulder
Igneous rocks are products of the cooling and crystallization of high temperature ...

using-topographic-maps-to-generate-topographic-profiles

Using Topographic Maps to Generate Topographic Profiles

Source: Laboratory of Alan Lester - University of Colorado Boulder
Topographic maps are &#34;plan-view&#34; representations of Earth&#39;s ...

determining-spatial-orientation-rock-layers-with-brunton

Determining Spatial Orientation of Rock Layers with the Brunton Compass

Source: Laboratory of Alan Lester - University of Colorado Boulder
Most rock units exhibit some form of planar surfaces or linear features. Examples ...

Making a Geologic Cross Section

Source: Laboratory of Alan Lester - University of Colorado Boulder
Geologic maps were first made and utilized in Europe, in the mid-to-late 18th century. ...

Use models to explain how mantle convection powers plate tectonics.

ESS.EES.2.1

Analyze and interpret data to predict locations of volcanoes and earthquakes based on plate boundaries.

ESS.EES.2.2

an-overview-of-alkenone-biomarker-analysis-for-paleothermometry

An Overview of Alkenone Biomarker Analysis for Paleothermometry

Source: Laboratory of Jeff Salacup&#160;- University of Massachusetts Amherst
Throughout this series of videos, natural samples were extracted and ...

Topographic Surveying and Contours

Topographic surveying is critical for documenting the Earth's surface, focusing on capturing elevations, slopes, and natural and man-made features. It is ...

Plotting of Topographic Maps

Topographic maps represent the Earth's surface features using contour lines, which connect points of equal elevation to create a two-dimensional ...

Methods of Obtaining Topography

Topography involves measuring and mapping land elevations, natural features, and artificial structures to create accurate representations of the terrain. ...

Use models to explain how plate tectonics influence topography.

ESS.EES.2.3

The Soil Ecosystem

Plants obtain inorganic minerals and water from the soil, which acts as a natural medium for land plants. The composition and quality of soil depend not ...

Conditions on Early Earth

What are Biogeochemical Cycles?

The most common elements in organic molecules, carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, are only available in the ecosystem in limited ...

The Water Cycle

The Earth&rsquo;s hydrosphere includes all of the areas where the storage and movement of water occurs. Since water is the basis of all living processes, ...

The Nitrogen Cycle

Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of ...

The Phosphorus Cycle

Unlike carbon, water, and nitrogen, phosphorus is not present in the atmosphere as a gas. Instead, most phosphorus in the ecosystem exists as compounds, ...

The Sulfur Cycle

Sulfur, an important element in the chemical makeup of proteins, is recycled through the atmosphere and aquatic and terrestrial environments. Found in the ...

Bioremediation

Bioremediation is the use of prokaryotes, fungi, or plants to remove pollutants from the environment. This process has been used to remove harmful toxins ...

Carry out investigations to explain how the rock cycle and rates of weathering, erosion, and soil formation influence Earth's systems.

ESS.EES.2.4

What is Climate?

Climate refers to the prevailing weather conditions in a specific area over an extended period. As the saying goes, &#8220;Climate is what you expect. ...

What is Weather?

Overview

Weather refers to the current state of atmospheric conditions at a specific time and place. Weather is temporary and is influenced by the ...

Variation of Atmospheric Pressure

Change in atmospheric pressure with height is particularly interesting. The decrease in atmospheric pressure with increasing altitude is due to the ...

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Analyze and interpret data to explain how volcanic activity influences changes in Earth's atmosphere, geosphere, biosphere, and hydrosphere.

ESS.EES.2.5

States of Water

Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the ...

The potential of hydrogen (pH) is a measure of the acidity or basicity of a water-based solution determined by the concentration of hydronium ions (H3O+). ...

Solvents

A solvent is a substance, most often a liquid, that can dissolve other substances. Here, the substance being dissolved is called a solute. When a solvent ...

Redox Reactions

Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another ...

Adhesion

Adhesion occurs when one type of molecule is attracted to a different molecule. Water exhibits adhesive properties in the presence of polar surfaces, such ...

Cohesion

Cohesion is the attraction between molecules of the same type, such as water molecules. Water molecules have an overall neutral charge but are polar ...

Specific Heat

The specific heat capacity of a substance refers to the energy required to increase the temperature of one gram of that substance by one degree Celcius. ...

Vaporization

The physical form of a substance changes by changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Role of Water in Human Biology

Water is the one of the most significant components of the human body; it plays a crucial role in several physiological activities because of its unique ...

solubility-equilibria-ionic-product-of-water

Solubility Equilibria: Ionic Product of Water

Water is a weak electrolyte and undergoes a small amount of self-ionization.
At any given temperature, the concentration of undissociated water is ...

Carry out investigations to explain the properties of water.

ESS.EES.3.1

Analyze how the geosphere is shaped by plate tectonics and the rock cycle.

Why Biodiversity Matters in Ecosystems

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