Learning Outcomes After studying this chapter, you should be able to answer the following questions:
• What are nine major terrestrial biomes, and what environmental conditions control their distribution?
• How does vertical stratification differentiate life zones in oceans?
• Why are coral reefs, mangroves, estuaries, and wetlands biologically important?
• What do we mean by biodiversity? List several regions of high biodiversity.
• What are four major benefits of biodiversity?
• What are the major human-caused threats to biodiversity?
• How can we reduce these threats to biodiversity?
In the end, we conserve only what we love. We will love only what we understand. We will understand only what we are taught. –Baba Dioum 5-
5.1 Terrestrial Biomes
Biodiversity- the number and variety of species.
Biomes- broad types of biological communities with characteristic types of environments that occur in different conditions of temperature and precipitation.
Figure 5.3 Biomes most likely to occur in the absence of human disturbance or other disruptions, according to average annual temperature and precipitation. Note: This diagram does not consider soil type, topography, wind speed, or other important environmental factors. Still, it is a useful general guideline for biome location.
Vertical zonation is a term applied to vegetation zones defined by altitude.
Annual temperature and precipitation levels in terrestrial biomes 5-
Tropical rainforests occur where rainfall is abundant — more than 200 cm (80 in.) per year—and temperatures are warm to hot year-round
Tropical savannas and grasslands are dry most of the year
Where there is too little rainfall to support forests, we find open grasslands or grasslands with sparse tree cover, which we call savannas.
Deserts are hot or cold, but always dry
Deserts occur where precipitation is uncommon and slight, usually with less than
Temperate grasslands have rich soils
As in tropical latitudes, temperate (midlatitude) grasslands occur where there is enough rain to support abundant grass but not enough for forests
Temperate forests can be evergreen or deciduous
These forests by are grouped by tree type, broad-leaved deciduous (losing leaves seasonally) or evergreen coniferous (cone-bearing).
The coniferous forests of the Pacific coast grow in extremely wet conditions. The wettest coastal forests are known as temperate rainforest, a cool, rainy forest often enshrouded in fog.
Boreal forests lie north of the temperate zone 5-
Tundra can freeze in any month
Compared to other biomes, tundra has relatively low diversity.
5.2 Marine Ecosystems
Most marine communities depend on photosynthetic organisms.
Phytoplankton: algae or tiny, free-floating photosynthetic plants that often support a marine food web.
Open ocean communities vary from surface to hadal zone 5-
Tidal shores support rich, diverse communities
Coral reefs are among the best-known marine systems, because of their extraordinary biological productivity and their diverse and beautiful organisms
Tidal shores continued: Mangroves
Mangroves are a diverse group of salt-tolerant trees that grow along warm, calm marine coasts around the world
Tidal shores continued: Estuaries & Salt Marshes
Estuaries are bays where rivers empty into the sea, mixing fresh water with salt water. Salt marshes, shallow wetlands flooded regularly or occasionally with seawater, occur on shallow coastlines, including estuaries
Tidal shores continued: Tide pools
Tide pools are depressions in a rocky shoreline that are flooded at high tide but retain some water at low tide.
5.3 Freshwater Ecosystems: Lakes 5-
Freshwater Ecosystems continued: Wetlands 5- Wetlands (swamps, marshes, & bogs) are shallow ecosystems in which the land surface is saturated or submerged at least part of the year.
Freshwater Ecosystems continued: Streams & Rivers
Streams form wherever precipitation exceeds evaporation and surplus water drains from the land.
As streams collect water and merge, they form rivers.
Biodiversity, the variety of living things.
Three kinds of biodiversity are essential to preserve ecological systems and functions:
genetic diversity is a measure of the variety of versions of the same genes within individual species
species diversity describes the number of different kinds of organisms within a community or ecosystem
ecological diversity means the richness and complexity of a biological community
Increasingly, we identify species by genetic similarity
Species are distinct organisms that persist because they can produce fertile offspring.
The phylogenetic species concept, which identifies genetic similarity, allows for asexual organisms and sexually reproducing ones that don’t normally encounter each other.
Biodiversity hot spots are rich and threatened 5-
5.5 Benefits of Biodiversity
All of our food comes from other organisms
Many wild plant species could make important contributions to human food supplies.
Rare species provide important medicines
More than half of all prescriptions contain some natural products.
Biodiversity can support ecosystem stability
Biodiversity has aesthetic and cultural benefits
5.6 What Threatens Biodiversity?
Extinction, the elimination of a species, is a normal process of the natural world.
Threats to biodiversity:
Habitat destruction is the main threat
Fragmentation reduces habitat to small, isolated patches
Invasive species are a growing threat
Pollution poses many different types of risk
Human population growth
Overharvesting & commercial collection
Predator and pest control
5.7 Endangered Species Management and Biodiversity Protection
Hunting and fishing laws protect reproductive populations
The endangered species act protects habitat and species
Endangered species act terminology
Endangered species are those considered in imminent danger of extinction
Threatened species are likely to become endangered, at least locally within the forseeable future.
Vulnerable species are naturally rare or have been locally depleted by human activities to a level that puts them at risk.
Keystone species are those with major effects on ecological functions and whose elimination would affect many other members of the biological community.
Indicator species are those tied to specific biotic communities or successional stages or environmental conditions.
Species Terminology continued…
Umbrella species require large blocks of relatively undisturbed habitat to maintain viable populations.
Flagship species are especially interesting or attractive organisms to which people react emotionally.
Controversy persists in species protection:
In 1995 the Supreme Court ruled that critical habitat—habitat essential for a species’ survival—must be protected, whether on public or private land.
An important test of the ESA occurred in 1978 in Tennessee, when construction of the Tellico Dam threatened a tiny fish called the snail darter.
Many countries have laws for species protection
Canada’s Committee on the Status of Endangered Wildlife in Canada (COSEWIC) of 1977 establishes rules for listing and protecting endangered species.
The European Union’s Birds Directive (1979) and Habitat Directive (1991).
Australia’s Endangered Species Protection Act (1992).
The Convention on Biological Diversity (1992) is an International agreement.
The Convention on International Trade in Endangered Species (CITES) of 1975.
Habitat protection may be better than species protection
By focusing on populations already reduced to only a few individuals, we spend most of our conservation funds on species that may be genetically doomed no matter what we do.
It is time to focus on a rational, continent-wide preservation of ecosystems that supports maximum biological diversity rather than a species-by-species battle for the rarest or most popular organisms.
1. Why did ecologists want to reintroduce wolves to Yellowstone
Park? What goals did they have, and have their goals
2. Describe nine major types of terrestrial biomes.
3. Explain how climate graphs (as in fig. 5.6) should be read.
4. Describe conditions under which coral reefs, mangroves,
estuaries, and tide pools occur.
5. Throughout the central portion of North America is a large
biome once dominated by grasses. Describe how physical
conditions and other factors control this biome.
Practice Quiz continued…
6. Explain the difference between swamps, marshes, and bogs.
7. How do elevation (on mountains) and depth (in water) affect
environmental conditions and life-forms?
8. Figure 5.15 shows chlorophyll (plant growth) in oceans and
on land. Explain why green, photosynthesizing organisms
occur in long bands at the equator and along the edges of
continents. Explain the very dark green areas and yellow/
orange areas on the continents.
9. Define biodiversity and give three types of biodiversity essential in preserving ecological systems and functions.
Practice Quiz continued…
10. What is a biodiversity “hot spot”? List several of them (see fig. 5.22).
11. How do humans benefit from biodiversity?
12. What does the acronym HIPPO refer to?
13. Have extinctions occurred in the past? Is there anything unusual about current extinctions?
14. Why are exotic or invasive species a threat to biodiversity? Give several examples of exotic invasive species (see fig. 5.27).
15. What is the Endangered Species Act? Describe some of the main arguments of its proponents and opponents.
16. What is a flagship or umbrella species? Why are they often important, even though they are costly to maintain?