chapter 7: biological diversity
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Chapter 7: Biological Diversity. What is Biological Diversity. Bio diversity refers to the variety of life forms in an area. Expressed as # of species in an area Or # of genetic types in an area. Biodiversity Definition: Variety of different species. Species Diversity : - PowerPoint PPT PresentationTRANSCRIPT
Chapter 7: Biological Diversity
What is Biological Diversity
Bio diversity refers to the variety of life forms in an area.– Expressed as # of species in an area – Or # of genetic types in an area
Biodiversity Definition: Variety of
different species.
Species Diversity:Number of different species and their relative abundances in a given area.
Genetic Diversity: Variety in the genetic makeup of organisms of a species that allow the species to reproduce and gain a competitive advantage
Ecosystem Diversity: The variety of forests, deserts, grasslands, oceans, lakes, etc.
Why Should We Care About Biodiversity?
Use Value: For the usefulness in terms of economic and ecological services.
Nonuse Value: existence, aesthetics, bequest for future generations.
Figure 10-3
Importance of Diversity Stability- stable environment Genetic reserves- genetic diversity Medicinal- medicines Agricultural- food Industrial- building homes; things we use Scientific- experimental; new technology Aesthetic- beautiful Ethical- what should we do regarding the
environment Religious- religious beliefs regarding
environment
Biological Evolution New species arise as a result
– of competition for resources – the difference among individuals in
their adaptations to environmental conditions
Four processes lead to evolution– Mutation, natural selection,
migration and genetic drift
Mutation Genes are inherited from one
generation to the next– Genes made up of DNA– DNA made up bases A,C,G,T
How these letters are combined determines the massage passed to a cell
Mutation When cells divide
– DNA is reproduced – Each cell gets a copy
If an error occurs in the reproduction of DNA it gets passed to new cells
DNA change = Mutation
Mutation
Natural Selection Some individuals may be better
suited to the environment than others.
Those better able to survive and reproduce leave more offspring.
Their descendants form a larger proportion of the next generation.
Natural Selection Four primary characteristics
– Genetic variability– Environmental variability– Differential reproduction that varied
with the environment– Influence of the environment on
survival and reproduction
Natural Selection The accumulation of changes may
lead to reproductive isolation– Resulting in a new species
Species = a group of individuals that can reproduce with each other.
Migration and Geographic Isolation
Two populations become geographically isolated for a long time– Enough change accumulates so that
they no longer reproduce– Two new species have formed– Migration important evo process
(e.g. Hawaii honey creeper and Darwin’s finches)
Adaptive Radiation Galapagos Islands
– Darwin observed numerous finches related to a single finch elsewhere
– Each with a different niche– Process called adaptive radiation
Founder Effect and Genetic Drift
Founder effect– Small # of individuals are isolated
from larger pop. Less genetic variation than original pop Which characteristics present affected
by chance Genetic drift is changes in freq of
a gene simply by chance Ind may NOT be better adapted
10 species; 100 ind, 87 elephants, 9 sp w/ 2 ind each
10 species; 100 ind, 10 ind each species
Species Diversity
Merely counting the number of species is not enough to describe biological diversity.
The Evolution of Life on Earth
Earliest fossils 3.5 billion years old– Photosynthetic relative of bacteria– Released large amounts of oxygen
into the atmosphere
The Evolution of Life on Earth
Cambrian Period 600 million years- 500 my
– Earliest multicellular organisms – Shells, gills, filters, efficient guts and
circulatory system.– Life remained in oceans
The Evolution of Life on Earth
Innovations for life on land– Structural support– Internal aquatic environment– Means for exchanging gases with air– A moist environment for
reproduction system
The Evolution of Life on Earth
Devonian Period– 420–360 million years ago– First animals on land =
crossopterygian– Gave rise to the amphibians
Still tied to water for reproduction Modern species include frogs, toads,
newts, limbless water “snakes”
Early Life on Land
The Evolution of Life on Earth
Reptiles– Freed from water by evolving a
watertight egg– Originate in the Carboniferous (375
mya)– Wide spread by the Jurassic (185
mya)– Two orders of dinosaurs that gave
rise to mammal and birds.
The Evolution of Life on Earth
Mammals– More capable
brain and faster metabolism
– Placental uterus one key to mammalian success