Biomes - Muhlenberg College · Biomes The biome is another major biogeographic pattern. It is a...
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Biomes The biome is another major biogeographic pattern. It is a kind of ecosystem, such as a desert, a tropical rain forest, a grassland. Here's how it worlcs: Similar environments pro- vide similar opportunities for life and similar constraints. As a result, similar environments lead to the evolution of or- ganisms similar in form and function (but not necessarily in genetic heritage or internal makeup) and similar ecosystems. This is lcnown as the rule of climatic n'milarity and leads to the concept of the biome. The close relationship between environment and kinds of life-forms is shown in Figure 8.4. Plants that grow in deserts of North America and East Afiicz illustrate the idea of a biome (see Figure 8.5). The desert euphorbia of South Africa loolzs similar to North American desert plants, but is not closely related to them. They belong to different biological families. Geographically isolated for 180 million years, they have been subjected to similar climates, which imposed similar stressrs and opened up similar ecological opportunities. On both continents, desert plants evolved to adapt to these stresses and poten- tials, and have come to look alilze and prevail in like habitats. The ancestral differences between these loolz-alike plants can be found in their flowers, fruits, and seeds, which change the least over time and thus provide the best clues to the genetic history of a species. The Joshua tree and saguaro cactus of North America and the giant Euphorbia of East and Southern Africa are td, have succulent green stems that replace the leaves as the major sites of photo- synthesis, and have spiny projections, but these plants are not closely related. The Joshua tree is a member of the agave family, the saguaro is a member of the cactus family, and the Euphorbia is a member of the spurge family. Their similar shapes result from evolution in similar desert &nates, a process lcnown as convergent evolution. The ~uphorbia and the Joshua tree are in the same biome but in different biotic provinces. They function similarly and have the same niche, but they are not closely related. So here is the difference between a biotic province and a biome: A biotic province is based on who is related to whom. A biome is based on niches and habitats. Species &hin a biotic province, in general, are more closely re- lated to each other than to species in other provinces. ; two different biotic provinces, the same ecolog- * i ical niche will be N e d with species that perform i 2 specific function and may look very similar to ! each other but have quite different genetic an- ' ! cestries. In this way, a biotic province is an ! evolutionary unit. The strong relationship between cli- ' mate and life suggests that if we know / the climate of an area, we can make a pretty good prediction about what biome will be found there, Excerpted from Botltin and Keller. 2007. EnvironmentalScience: Earth as a livingplanet. Wiley. Mediterranean ' what its approximate biomass (amount of living matter) and - lncreasng aridity - production will be, and what Figure 8.4 . SimpEed diagam of the relationship between precipirauon and latitude and Earrh's ma- the shapes and forms of d ~ ~ - jor land biomes. Here, latimde sew= as an index of average rempeiature, so latitude can be repiaced by inant organisms will be.l2> l3 average temperature in this diagram. [Some Figwe 274, p. 293, &om Phyncal Geoflaphy ofthe Global Environment by Harm de Blij, Peter 0. Muller, and Richard S. WJliams, edited by Harm de BLij, capy- right 2004 by Oxford University Press, Inc. Uscd by permission of Oxford Univenity Press, Inc.]
Transcript of Biomes - Muhlenberg College · Biomes The biome is another major biogeographic pattern. It is a...
Biomes
The biome is another major biogeographic pattern. It is a kind of ecosystem, such as a desert, a tropical rain forest, a grassland. Here's how it worlcs: Similar environments pro- vide similar opportunities for life and similar constraints. As a result, similar environments lead to the evolution of or- ganisms similar in form and function (but not necessarily in genetic heritage or internal makeup) and similar ecosystems. This is lcnown as the rule of climatic n'milarity and leads to the concept of the biome. The close relationship between environment and kinds of life-forms is shown in Figure 8.4.
Plants that grow in deserts of North America and East Afiicz illustrate the idea of a biome (see Figure 8.5). The desert euphorbia of South Africa loolzs similar to North American desert plants, but is not closely related to them. They belong to different biological families. Geographically isolated for 180 million years, they have been subjected to similar climates, which imposed similar stressrs and opened up similar ecological opportunities. On both continents, desert plants evolved to adapt to these stresses and poten- tials, and have come to look alilze and prevail in like habitats.
The ancestral differences between these loolz-alike plants can be found in their flowers, fruits, and seeds, which change the least over time and thus provide the best clues to the genetic history of a species. The Joshua tree and saguaro cactus of North America and the giant Euphorbia of East and Southern Africa are td,have succulent green stems that replace the leaves as the major sites of photo- synthesis, and have spiny projections, but these plants are not closely related. The Joshua tree is a member of the agave family, the saguaro is a member of the cactus family, and the Euphorbia is a member of the spurge family.
Their similar shapes result from evolution in similar desert &nates, a process lcnown as convergent evolution. The ~uphorbia and the Joshua tree are in the same biome but in different biotic provinces. They function similarly and have the same niche, but they are not closely related.
So here is the difference between a biotic province and a biome: A biotic province is based on who is related to whom. A biome is based on niches and habitats. Species &hin a biotic province, in general, are more closely re- lated to each other than to species in other provinces.
; two different biotic provinces, the same ecolog- * i ical niche will be N e d with species that perform i 2 specific function and may look very similar to ! each other but have quite different genetic an- ' ! cestries. In this way, a biotic province is an ! evolutionary unit.
The strong relationship between cli- ' mate and life suggests that if we know
/ the climate of an area, we can make a pretty good prediction about what biome will be found there,
Excerpted from Botltin and Keller. 2007. EnvironmentalScience: Earth as a livingplanet. Wiley.
Mediterranean
'
what its approximate biomass (amount of living matter) and - lncreasng aridity -production will be, and what
Figure 8.4 .SimpEed diagam of the relationship between precipirauon and latitude and Earrh's ma- the shapes and forms of d ~ ~ -
jor land biomes. Here, latimde sew= as an index of average rempeiature, so latitude can be repiaced by inant organisms will be.l2> l3 average temperature in this diagram. [SomeFigwe 274, p. 293, &om Phyncal Geoflaphy ofthe Global
Environment by Harm de Blij, Peter 0.Muller, and Richard S.WJliams, edited by Harm de BLij, capy-right 2004 by Oxford University Press, Inc. Uscd by permission of Oxford Univenity Press, Inc.]
