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. The evolution of life is linked to the physical and chemical evolution of the earth.

2. 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.

3. 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

- 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.

Fig. 4-5, p. 88

135 million years ago

Present65 million years ago

225 million years ago

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)

-

species diversity

genetic diversity

ecosystem diversity

functional diversity

1.8 million of the earth’s 4-

20 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?

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..

1. The range of tolerance for various physical and chemical condisitons

2. The types of resources it uses, such as food or nutrient requirements

3. How it interacts with other living and nonliving components of the ecosystems in which it is found

4. 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

Fundamental Niche- 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.

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

Fig. 4-12, p. 93

Tertiary

Bar width represents relative

number of living speciesEra Period

Species and families

experiencing

mass extinction

Millions of

years ago

Ordovician: 50% of animal

families, including many

trilobites.

Devonian: 30% of animal

families, including agnathan and

placoderm fishes and many

trilobites.

500

345

Cambrian

Ordovician

Silurian

Devonian

Extinction

Extinction

Pa

leo

zo

icM

es

ozo

icC

en

ozo

ic

Triassic: 35% of animal families,

including many reptiles and marine

mollusks.

Permian: 90% of animal families,

including over 95% of marine

species; many trees, amphibians,

most bryozoans and brachiopods,

all trilobites.Carboniferous

Permian

Current extinction crisis caused

by human activities. Many species

are expected to become extinct

within the next 50–100 years.

Cretaceous: up to 80% of ruling

reptiles (dinosaurs); many marine

species including many

foraminiferans and mollusks.

Extinction

Extinction

Triassic

Jurassic

Cretaceous

250

180

65Extinction

ExtinctionQuaternary Today

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).