Textbook Notes (363,237)
Canada (158,278)
Biology (652)
BIOLOGY 1M03 (198)
Chapter 55

Unit 9 - Chapter 55- Bio 1M03 .docx

4 Pages
Unlock Document

McMaster University
James S Quinn

Bio 1M03 Unit Nine: Ecology Chapter 55: Biodiversity and Conservation Biology 55.1 What Is Biodiversity? Biodiversity Can Be Measured and Analyzed at Several Levels?  Biologists recognize and analyze biodiversity on three levels 1. Genetic Diversity – the total genetic information contained within all individuals of a species o Measures as the number and relative frequency of all alleles present in a species o No two members of the same species are genetically identical – each species is the repository of an immense array of alleles o Mutations can increase genetic diversity 2. Species Diversity – variety of species on earth o Measured by quantifying the number and relative frequency of species in a particular region o Taxonomic diversity – documented by estimating phylogenies; want to know evolutionary relationships in addition to number and relative frequency of species present o Natural selection, genetic drift and gene flow may eliminate certain alleles or change their frequency – leads to an increase or decrease in species diversity 3. Ecosystem Diversity – variety of biotic communities in a region along with abiotic components (soil, water, nutrients) o Measurement is difficult – ecosystems do not have sharp boundaries o Ecosystems – complex and dynamic assemblages of organisms that interact with each other and their nonliving environment o Attempts to measure – focus on capturing the array of biotic communities in a region along with variation in the physical conditions present o Changes in climate or other physical conditions or the evolution of new species and their interactions can result in the formation of new ecosystems o Disturbances can destroy ecosystems Environmental Sequencing: A New Approach to Quantifying Genetic Diversity How Many Species Are Living Today?  ~1.5 million species have been documented – only a small fraction of the number actually present o Eg/ Over 300 000 plant species; 6:1 fungal to plant ratio  suggests that 1.65 million species of fungi exist even though only 80 000 documented  Two general approaches to estimate total number of species on earth 1. Taxon-Specific Surveys – based on intensive surveys of species rich groups at small sites o Eg/ Terry Erwin and J.C. Scott  Estimated the number of insect species that live in the canopy of a single tropical tree  Used an insecticidal fog to knock down insects from the top of a Luehea Seemannii tree  Identified over 900 species of beetles among the individuals that fell; most new to science  Used data as an indicator of global arthropod diversity o Eg/ Philippe Bouchet and colleagues  Conducted massive survey of marine mollusks in coral-reef habitats along west coast of New Caledonia (tropical island in SW Pacific Ocean) 2. All Taxa Surveys – based on attempts to identify all of the species present in a particular region 55.2 Where Is Biodiversity Highest?  In most taxonomic groups, species richness is highest in the tropics and declines toward the poles o Tropical Rainforests are species rich – 7% of earths land; contains ~50% of all species  Hotspots – areas that are much more species rich that others  Endemic Species – species that are found in an area, but no where else  Identify regions of the world that are in urgent need of conservation actions – areas where efforts to preserve habitats would have the highest return on investment o Eg/ Protecting hotspots 55.3 Threats to Biodiversity Bio 1M03  Although extinction is natural due to climate change, disease competition and habitat alteration – the rate at which extinction is occurring is concerning  Species are vanishing faster now than at any other time in Earth’s history (100 – 1000 times greater than background rate (average rate) in the fossil record over the past 550 million years)  Extinctions caused by rapidly growing human population (increasing by ~77 million people/year) Humans Have Affected Biodiversity Throughout History  Humans have a poor record of preserving species they depend on for survival  Eg/ Easter Island o European explorers arrived on Easter Island in 1722 – 1000 lived there; island was treeless and dotted with gigantic stone statues o Island had once been covered with lush forest (palm trees) – rapid decline in tree pollen and fauna coincided with arrival of first human settlers o Upon arrival of human population – island was brimming with natural resources; people had leisure time to make statues and roll them into place using logs o After deforestation was complete – could not make canoes; no longer hunted dolphin and less fishing, Current Threats to Biodiversity  Most extinctions over the past 1000 years o Took place on islands o Caused by overhunting or the introduction of exotic species (nonnative competitors, diseases or predators)  Endangered species – species almost certain to go extinct unless effective conservation programs are put in place o Now live in continents rather than islands o Habitat destruction has taken the place of overhunting and species introduction  Virtually all endangered species are affected by more than once factor  Habitat loss is the most important factor in the decline of species – significant issue for over 90% of endangered species in terrestrial environments  Overharvesting is the dominant problem for marine species  Pollution plays a large f=role for freshwater species  Non human factors – predation, competition with native species, natural disturbances (fires, droughts), narrow niches Habitat Destruction  Humans cause habitat destruction by logging and burning forests, damming rives, dredging or filling estuaries and wetlands, plowing prairies, grazing livestock, excavating minerals, building structures (houses, roads etc.)  Deforestation – one of the most important types of habitat destruction; conversion of primary forests to agricultural fields and human settlements Habitat Fragmentation  Human activities fragment large, contiguous areas of natural habitats into small, isolated fragments 1. Reduces habitats to a size that is too small to support some species o Especially true for keystone predators which need vast natural spaces in which to feed, find mates and reproduce successfully 2. Reduces the ability of individuals to disperse from one habitat to another (due to creating islands of habitats in a sea of human-dominated landscapes) o Forcing many species into the metapopulation structure o Small, isolated populations that make up a metapopulation are much more likely than large populations to  Be wiped out by catastrophic events such as storms, disease outbreaks or fires  Suffer from inbreeding depressio
More Less

Related notes for BIOLOGY 1M03

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.