Chapter 4

Biodiversity and Evolution

Chapter 6Evolution 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)

How Did Life Emerge on the Earth?

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)

Biological Evolution

• By Natural Selection, explains how life changes over timeAdaptation or Adaptive traits enables an organism to survive through natural

selectionto reproduce under prevailing

environmentalconditions

Geological Processes and Climate Change affect……………

• Huge flows of molten rock within the earth’s interior break into surfaces into a series of gigantic solid plates – TECTONIC PLATES

• Plates have drifted atop planets mantle• Locations of continents and oceans basin influence earth’s climate• species move, adapt to new environments• earthquakes, volcanic eruptions

Climate Change

• alternate periods of heating and cooling• advance and retreats of ice sheets at

high latitudes over northern hemispheres

Catastrophic events

• collision events between earth and large

asteroids

Biodiversity Speciation

– geographic isolation– reproductive isolationExtinction

endemic species more vulnerableBackground Extinction – 1-5 /million speciesMass Extinction – 5 extinctions 20-60 million years apart in the last 500 million years (20-60 million years apart)

-

How did humans become so powerful?

• strong opposable thumbs• walk upright• powerful brain – allow us to live more sustainably

Identified……….

1.8 million of the earth’s 4-20 million species

Components………

species diversity

genetic diversity

ecosystem diversity

functional diversity

Importance of species diversity

• 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

What determines the number of species in an

ecosystem

•size and degree of isolation

•larger islands have more species than smaller

Theory of Island Biogeography

•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

continued…..•2 important variables•size of the island, distance from the mainland source of immigrant species

•smaller island - lower species density

Evolution and AdaptationWhat is evolution?-AKA biological evolution-The change in a population’s genetic

makeup through sucesive generations.

What is theory of evolution?-All species descended from earlier,

ancestral species.

Types of biological evolution…-microevolution-macroevolution -gene pool – sum of all genes possessed

by the individuals of the population.- Alleles – genes with more than two or

more different molecular forms. (p. 141)

How Does the Ecological Niche Relate to Adaptation?

• Evolution by natural selection leads to a remarkable fit between organisms and their environment. In terms of the ecological niche of a particular species, this fit involves having a set of traits that enables individuals to survives and reproduce in a particular environment. Species that have similar niches tend to evolve similar sets of traits, even if they are unrelated species growing in different parts of the world. (p. 145)

What Limits Adaptation?

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)

Microevolution

- 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)

Macroevolution• 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.

Sustainability and Evolution

• 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.

Adaptation and the Ecological 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)

The Ecological Niche

• 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.

What is the Difference Between Fundamental Niche and Realized

Niche?

• 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.

Some General Types of Species...

• Native species: species that normally live & thrive in a particular ecosystem.

• Nonnative species, Exotic species, Alien species: other species that migrate into an ecosystem or are introduced into an ecosystem by humans.

Some general species continued...

• Indicator species: species that serve as early warnings that a community or an ecosystem is being damaged.

Some general species continued...

• Keystone Species: species that play roles affecting many other organisms in an ecosystem.

* Dung beetle

* Sea otters

* Gopher tortoises

* Bats