Evolution and Biodiversity

What is biodiversity? *Biodiversity is the variety of earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life. Each cell contains… 1. Genes, (containing specific DNA molecules) which determine what form the cell will take and its functions. 2. Other parts, which protect the cell and carry out the instructions encoded in the cell’s DNA molecules. What’s the difference between eukaryotic and prokaryotic? Eukaryotic cells are surrounded by a membrane and have a nucleus and several other internal parts, and all bacterial cells are prokaryotic, without a distinct nucleus or other internal parts enclosed by membranes. (p. 133 and p. 134)

 During the 3.7 billion

years since life arose, the average surface temperature of the earth has remained within the range of 10-20oC.

Figure 4-1

 1 billion years of chemical change to form the first cells,

followed by about 3.7 billion years of biological change.

Figure 4-2

1.

2.

3.

The evolution of life is linked to the physical and chemical evolution of the earth. Life on earth evolved in two phases over the past 4.7 – 4.8 billion years… Chemical Evolution (1 billion years) of the organic molecules, biopolymers, and systems of chemical reactions needed to form the first protocells and Biological Evolution (3.7 billions years) of single-celled organisms and then multicellular organisms. Over time, it is believed that the protocells evolved into single-celled, bacterialike prokaryotes having the properties we describe as life. (p.140)

 This has led to the

variety of species we find on the earth today.

Figure 4-2

 Biological evolution by natural selection involves the

change in a population’s genetic makeup through successive generations.  genetic variability  Mutations: random changes in the structure or number of

DNA molecules in a cell that can be inherited by offspring.

 By Natural Selection, explains how life

changes over time Adaptation or Adaptive traits enables an organism to survive through natural selection to reproduce under prevailing environmental conditions

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Microevolution works through a combination of four processes that change the genetic composition of a population:

 Mutation – involving random changes in the structure or number of DNA

molecules in a cell and is the ultimate source of genetic variability in a population.  Natural selection – occurs when some individuals of a population have

genetically based traits that cause them to survive and produce more offspring than other individuals  Gene flow – which involves movement of genes between populations and

can lead to changes in the genetic composition of local populations.  Genetic drift – involves changes in the genetic composition of a population

by chance and is especially important for small populations. (p. 142)



What is macroevolution?

Macroevolution is concerned with how evolution takes place above the level of species and over much longer periods than microevolution, and macro evolutionary patterns include genetic persistence, genetic divergence, and genetic loss. Speciation – under certain circumstances natural selection can lead to an entirely new species. Extinction – when all of one species is no longer existent.

 Earth is constantly changing, and

throughout the earth’s history the atmosphere has changed, the climte has changed, the geography has changed he types and numbers of organisms have changes, and continental drift has changed the positions of the earth’s continents.  Biologists estimate that the current

human-accerlated extinction rate of species is 1,000 to 10,000 times higher than natural extinction rates.

 Three conditions are necessary for biological evolution:  Genetic variability, traits must be heritable, trait must lead

to differential reproduction.  An adaptive trait is any heritable trait that enables an

organism to survive through natural selection and reproduce better under prevailing environmental conditions.

 Interacting species can engage in a back and forth genetic

contest in which each gains a temporary genetic advantage over the other.  This often happens between predators and prey species.

 New species can arise through hybridization.  Occurs when individuals to two distinct species crossbreed

to produce an fertile offspring.  Some species (mostly microorganisms) can exchange

genes without sexual reproduction.  Horizontal gene transfer

1.

A change in environment conditions can lead to adaptation only for traits already present in the gene pool of a population.

2.

Because each organism must do many things, its adaptations are usually compromises

3.

Even if a beneficial heritable trait is present in a population, that population’s ability to adapt can be limited by its reproductive capacity.

4.

Even if a favorable genetic trait is present in a population, most of its members would have to die or become sterile so that individuals with the trait could predominate and pass the trait on. (p. 146)

 A population’s ability to adapt to new environmental

conditions through natural selection is limited by its gene pool and how fast it can reproduce.  Humans have a relatively slow generation time (decades)

and output (# of young) versus some other species.

 Evolution through natural selection is about the most

descendants.  Organisms do not develop certain traits because they need

them.  There is no such thing as genetic perfection.

 The movement of solid (tectonic) plates making up the

earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones.  The locations of continents and oceanic basins influence

climate.  The movement of continents have allowed species to move.

225 million years ago

65 million years ago

135 million years ago

Present Fig. 4-5, p. 88

 Changes in climate throughout the earth’s history have

shifted where plants and animals can live.

Figure 4-6

 Asteroids and meteorites hitting the earth and upheavals

of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.

Speciation  geographic isolation  reproductive isolation Extinction endemic species more vulnerable Background Extinction – 1-5 /million species Mass Extinction – 5 extinctions 20-60 million years apart in the last 500 million years (20-60 million years apart)

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species diversity genetic diversity ecosystem diversity functional diversity

1.8 million of the earth’s 420 million species

 species richness – number of different species  species evenness- relative abundance of

individuals within each of those species  species diversity varies with geographic location  species rich ecosystems are productive and sustainable

 size and degree of isolation

 larger islands have more species

than smaller

 number of species found on the

island determined by (a) immigration rate of species to the island from other inhabited areas  and (b) extinction rate of species established on the island

Theory of Island Biogeography

Number of species related to size of the island

 2 important variables  size of the island, distance from

the mainland source of immigrant species  smaller island - lower species density

 Each species in an ecosystem has a specific role or way of

life.  Fundamental niche: the full potential range of physical,

chemical, and biological conditions and resources a species could theoretically use.  Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.

What is the ecological niche? 

1. 2. 3.

4.

Ecological niche is the species’ way of life or functional role in an ecosystem. A species’s niche involves everything that affects its survival and reproduction. This includes.. The range of tolerance for various physical and chemical condisitons The types of resources it uses, such as food or nutrient requirements How it interacts with other living and nonliving components of the ecosystems in which it is found The role it plays in the flow of energy and cycling of matter in an ecosystem. (p. 145)

 Each species has a particular ecological niche or

role it plays in ecosystem.  Niche of species differs from its habitat-- actual physical location where organisms making up species live.  Ecological niche can be defined by ranges of conditions and resources where organisms can live.

 Generalist species

tolerate a wide range of conditions.  Specialist species can only tolerate a narrow range of conditions.

Figure 4-7

full potential range of conditions and resources it could theoretically use if there weren’t direct competition from other species. Realized Niche- parts of the fundamental niche of a species actually used by that species.

 Fundamental Niche-



 350 million years old  3,500 different species  Ultimate generalist  Can eat almost anything.  Can live and breed almost

anywhere.  Can withstand massive radiation.

Figure 4-A

 Resource partitioning reduces competition and allows

sharing of limited resources.

Figure 4-8

 Each species has a beak

specialized to take advantage of certain types of food resource.

Figure 4-9

 Speciation: A new species can arise when member of a

population become isolated for a long period of time.  Genetic makeup changes, preventing them from producing

fertile offspring with the original population if reunited.

 …can lead to reproductive isolation, divergence of gene

pools and speciation. Figure 4-10

 Extinction occurs

when the population cannot adapt to changing environmental conditions.

The

golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate. Figure 4-11

Cenozoic

Era

Period

Millions of years ago

Quaternary

Today

Tertiary 65

Mesozoic

Cretaceous Jurassic 180 Triassic

Species and families experiencing mass extinction Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct Extinction within the next 50–100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks.

Bar width represents relative number of living species

250

Extinction

345

Extinction

Permian

Paleozoic

Carboniferous

Devonian

Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.

Silurian Ordovician Cambrian

500

Extinction

Ordovician: 50% of animal families, including many trilobites. Fig. 4-12, p. 93

 The scientific consensus is that human activities are

decreasing the earth’s biodiversity.

Figure 4-13

 We have used artificial selection to change the genetic

characteristics of populations with similar genes through selective breeding.  We

have used genetic engineering to transfer genes from one species to another. Figure 4-15

 GMOs

use recombinant DNA 

genes or portions of genes from different organisms.

Figure 4-14

 Biologists are learning to rebuild organisms from their

cell components and to clone organisms.  Cloning has lead to high miscarriage rates, rapid aging,

organ defects.  Genetic engineering can help improve human

condition, but results are not always predictable.  Do not know where the new gene will be located in the

DNA molecule’s structure and how that will affect the organism.

 There are a number of privacy, ethical, legal and

environmental issues.  Should genetic engineering and development be regulated?  What are the long-term environmental consequences?

 We lack:  strength, speed, agility.  weapons (claws, fangs), protection (shell).  poor hearing and vision.

 We have thrived as a species because of our:  opposable thumbs, ability to walk upright, complex brains

(problem solving).