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Patterns of biodiversity

Biodiversity is not evenly distributed on the planet. Lake Victoria contained almost 500 species of cichlids (only one family of fishes present in the lake) before the introduction of an exotic species in the 1980s and 1990s caused a mass extinction. All of these species were found only in Lake Victoria, which is to say they were endemic. Endemic species are found in only one location. For example, the blue jay is endemic to North America, while the Barton Springs salamander is endemic to the mouth of one spring in Austin, Texas. Endemics with highly restricted distributions, like the Barton Springs salamander, are particularly vulnerable to extinction. Higher taxonomic levels, such as genera and families, can also be endemic.

Lake Huron contains about 79 species of fish, all of which are found in many other lakes in North America. What accounts for the difference in diversity between Lake Victoria and Lake Huron? Lake Victoria is a tropical lake, while Lake Huron is a temperate lake. Lake Huron in its present form is only about 7,000 years old, while Lake Victoria in its present form is about 15,000 years old. These two factors, latitude and age, are two of several hypotheses biogeographers have suggested to explain biodiversity patterns on Earth.

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Biogeography

Biogeography is the study of the distribution of the world’s species both in the past and in the present. The work of biogeographers is critical to understanding our physical environment, how the environment affects species, and how changes in environment impact the distribution of a species.

There are three main fields of study under the heading of biogeography: ecological biogeography, historical biogeography (called paleobiogeography), and conservation biogeography. Ecological biogeography studies the current factors affecting the distribution of plants and animals. Historical biogeography, as the name implies, studies the past distribution of species. Conservation biogeography, on the other hand, is focused on the protection and restoration of species based upon the known historical and current ecological information. Each of these fields considers both zoogeography and phytogeography—the past and present distribution of animals and plants.

One of the oldest observed patterns in ecology is that biodiversity in almost every taxonomic group of organism increases as latitude declines. In other words, biodiversity increases closer to the equator ( [link] ).

 The number of amphibian species in different areas is specified on a world map. The greatest number of species, 61-144, are found in the Amazon region of South America and in parts of Africa. Between 21 and 60 species are found in other parts of South America and Africa, and in the eastern United States and Southeast Asia. Other parts of the world have between 1 and 20 amphibian species, with the fewest species occurring at northern and southern latitudes. Generally, more amphibian species are found in warmer, wetter climates.
This map illustrates the number of amphibian species across the globe and shows the trend toward higher biodiversity at lower latitudes. A similar pattern is observed for most taxonomic groups.

It is not yet clear why biodiversity increases closer to the equator, but hypotheses include the greater age of the ecosystems in the tropics versus temperate regions, which were largely devoid of life or drastically impoverished during the last ice age. The greater age provides more time for speciation. Another possible explanation is the greater energy the tropics receive from the sun versus the lesser energy input in temperate and polar regions. But scientists have not been able to explain how greater energy input could translate into more species. The complexity of tropical ecosystems may promote speciation by increasing the habitat heterogeneity    , or number of ecological niches, in the tropics relative to higher latitudes. The greater heterogeneity provides more opportunities for coevolution, specialization, and perhaps greater selection pressures leading to population differentiation. However, this hypothesis suffers from some circularity—ecosystems with more species encourage speciation, but how did they get more species to begin with? The tropics have been perceived as being more stable than temperate regions, which have a pronounced climate and day-length seasonality. The tropics have their own forms of seasonality, such as rainfall, but they are generally assumed to be more stable environments and this stability might promote speciation.

Questions & Answers

maitrocondriya kya hota hai
Husna Reply
distinguish between properties and characteristics
Elee Reply
what are organelles
Elee
what is biology
Prevail Reply
biology is science that studies life
Elee
it's the study of living and non living things
now that we have an estimate for the diameter of the cell.what estimate can we make about the volume of the cell?
faxhood Reply
why too much insulin result in low blood sugar
Leri Reply
For example, too much exercise can cost you to lose to much weight. Too much insulin will pull to much sugar out of your systemic system into your cells.
Eric
difference between DNA and RNA
Eyitayo Reply
DNA is deoxyribonuclaic acid. Deoxy refers to a lack of oxygen. The Ribose moity is missing an OH group. I think it is missing from the second C of the ring. RNA is ribonucleic acid. DNA has our genetic code in on it. RNA is translated from DNA and carries the blue print for protein synthesis.
Eric
The OH group on RNA prevents it from being reactive. But it is very unstable though. Would you want such a power tool floating around in your body, no. And you have three types of RNA: mRNA, tRNA and rRNA. Please let me know it this helped?😄
Eric
o
Browse
Eric answered this question perfectly
what determines the aeration level in the soil
Shola Reply
what is homeostasis?
Sarita Reply
It means balance in a biological system.
Eric
What is biology
Don Reply
Biology z the study of life
GOLDEN
what's biology
buran
biology is the study of living nd none living organism
Chinaza
Biology is the study of life
Quadri
yes Sir
Said
what's cell biology
Prince
biology is the study of life
Raheal
what is asexual reproduction,?
Awoi Reply
A type of reproduction which does not involve the fusion of gametes or a change in the number of chromosomes
Serena
Reproduction without sex... In which form a single organism or cell makes a copy of itself.
Serena
Please explain the concept of mitosis and meiosis
Serena
I guess you could use it for study buddies and brushing up on what you need to
Serena
what is mitosis
Klp
Asexual reproduction?
Serena
why pepsin and trypsin released in active form?
Yacqub
mitosis is the type cell division in which two daughter cells have same no. of chormosomes
syed
Hi
Don
chromosome number remains the same in mitosis
mc
Ello
Henry
Hii
Nikky
Yrr help me.
Nikky
Physical chemistry..... Koi h jo mujhe physical chem ki notes send kr ske
Nikky
what is asexual reproduction
Targbe
what makes golgi body in plants
Abdulkareem Reply
name the membrane of the plants
Abdulkareem
how can turners syndrome be corrected before birth
Balinda
which animal survive from being preyed just because of being humble, slow, and not aggressive
Balinda
Plants have golgi body's also. Plants are eukaryotic cells. And membrane bound organelles are a characteristic of eukaryotic cells. Moreover golgi body's are creatted from the ER. Also do not forget plants have plastids and animal cells do not.
Eric
During organs transplantation, the organs cannot be taken from just anybody since the graft would be rejected sooner or later due to
Liter Reply
Non-MHC compatibility on the organ and an attack from the patient's immune system.
Eric
what makes golgi body in plants
Abdulkareem
why trypsin and pepsin released in active form
Yacqub
Let us remember MHC'S on our cells. This is how our cells determine self from n o n s e l f. Transplanted tissue has to have a certain amount markers. These have to match to the recipiant's markers. Even with this, immunosuppresant medacine is prescribed to the recipient.
Eric
Even with these measures the body may still reject the transport. This can occur even after the recipient excepting the transport for some time.
Eric
what is integument system
Joy Reply
This system is our skin. This includes the skin lining our alimentary system which includes the tissue from our mouth to our anus. Our skin is our largest organ system. It is mostly made up of epithelial tissue.
Eric
Cellular respiration
Lucy Reply
This is how our cells make energy. They use glucose + oxygen. There are other facors involves also. But these are the main two reactant used, for aerobic respiration. The main product is ATP. ATP is a high energy molecule which is paramount for life.
Eric
what are the characteristics of living things
Ruth Reply
Movement Respiration Nutrition/Feeding Irritability/Sensitivity Growth Excretion Reproduction Deat/Life span
Hashim
What makes children from the same father and mother sometimes don't look alike?
Hashim
One of the main one's is the abilit reproduce. That is why viruses are not considered living. Because they do not have the ability to replicate on they own.
Eric

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Source:  OpenStax, Concepts of biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11487/1.9
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