Chapter 4 Biodiversity and Evolution

Section 4.1What is biodiversity and why is it important

Core Case Study : Why should we protect sharks Sharks play a crucial role in the oceanic world and many are

killed because we fear them or for there meat, skin, and livers.

Biodiversity Is a Crucial Part of the Earth’s Natural Capital Biological diversity/ biodiversity: variety of the earths species

or varying life-forms the genes they contain the ecosystems in which they live, and the ecosystem processes of energy flow and nutrient cycling that sustain all life

Species: set of individuals that can mate and produce fertile offspring. Estimated that there are 10-14 million species Up to half of the worlds plant and animal species live in tropical

rain forest

Species diversity Genetic Diversity: enables life on the earth to adapt to and

survive dramatic environmental changes Ecosystem Diversity: earths variety of deserts, grasslands,

forest, mountains, oceans, lakes, rivers, and wetlands Each of these ecosystems is a storehouse of genetic and species

biodiversity Biomes: large regions such as forest, deserts, and

grasslands with distinct climates and certain species (especially vegetation) adapted to them

Biodiversity Functional Diversity: the variety of processes such as energy flow

and matter cycling that occur within ecosystems as species interact with one another in food chains and webs.

The earths biodiversity is a vital part of the natural capital Keeps us alive/ supports economy

Biodiversity Provides Biodiversity is used to provide

Food Wood/ energy from it Fibers Biofuels Medicines

Plays a critical role in preserving the quality of the air/water maintaining fertility of topsoil, decomposing and recycling waste, and controlling populations of species that humans consider to pest

Helps sustain life on earth

Section 4.2 How does the Earth’s Life change over time

Biological Evolution by Natural Selection Explains How life Changed over Time Most of what we know from earths history comes from fossils Fossils: mineralized or petrified replicas of skeletons bones

teeth, shells, leaves, and seeds, or impressions of such items found in rocks

Fossil Record: entire body of evidence gathered using these methods which is uneven and incomplete Fossils found so far represent 1% of all species that have ever

lived Biological evolution: the process whereby earth’s life

changes over time through changes in the genetic characteristics of populations.

Darwin and Wallace Independently proposed the concept of natural selection as a

mechanism for biological evolution Observed that individual organisms must struggle constantly to

survive by getting food, water, and other resources. Based on the observations they described a process known as

natural selection: Individuals with certain traits are more likely to survive and reproduce

under a particular set of environmental conditions than are those without traits.

Biological Evolution through Natural Selection has become an important scientific theory that explains how life is so diverse today.

Evolution by Natural Selection Works through Mutations and Adaptions

Populations not individuals evolve by becoming genetically different First Step is the development of genetic variability: variety in the genetic makeup of

individuals in a population Mutation: random changes in DNA molecules of a gene that can be inherited by offspring

which then result in heritable trait: which can be passed from one generation to another

Adaptive trait: any heritable trait the improves the ability of an individual organism to survive and to reproduce at a higher rate

Differential Reproduction: enables individuals with the trait to produce more surviving offspring than other members of the population produce

Scientific concept of natural selection explains how popuations adapt to changes in environmental conditions

Process of biological evolution by natural selection Genes mutate Individuals are selected Populations evolve such that they are better adapted to

survive and reproduce under existing environmental conditions

Case Study: How did humans become such a powerful species Humans have survived and thrived because of certain traits

such as opposable thumbs, ability to walk upright and a complex brain.

Adaption through natural selection has limits There are two limitations on adaptation through natural

selection 1st : Change in environmental conditions can lead to such an

adaption only for genetic traits already present in a populations gene pool or for traits resulting from mutations which occur randomly

2nd: Even if a beneficial heritable trait is present in a population the populations ability to adapt may be limited by its reproductive capacity

Three Common Myths about Evolution through Natural Selection “Survival of the fittest” means “survival of the strongest”

Fitness is a measure of reproductive success not strength Organisms develop traits because they need them Species become more perfectly adapted

Section 4.3

How do geological processes and climate change affect evolution

Geological Processes Affected Natural Selection Tectonic Plates changed earths surface This fact has two important effects on the evolution and

distribution of life the earth 1st: locations (latitudes) of continents and oceanic basins have

greatly influenced the earths climate and thus helped to determine where plants and animals can live

2nd: the movement of continents has allowed species to move, adapt to new environments and form new species through natural selection.

Tectonic Plates Continents join= population disperse/adapt to new areas Continents separate= populations must evolve under isolated

conditions or become extinct. Sudden movements can cause earthquakes and volcanic

eruptions can affect biological evolution.

Climate Change and Catastrophes Affect Natural Selection Long term climate changes have a major effect on biological

evolution by determining where different types of plants and animals can survive and thrive and by changing the locations of different types of ecosystems

There has been estimated 3 collisions during the 3.5 million years that earth has had life existence

Section 4.4

How do speciation, extinction, and human activities affect biodiversity

How do new species evolve Speciation: one species splits into two or more different

species Most common way in which speciation occurs in two stages

1st:Geographic isolation 2nd: Reproductive isolation

Geographic Isolation: different groups or the same population of species become physically isolated from one another for a long period of time

Reproductive Isolation: mutation and change by natural selection operate independently in the gene pools or geographically isolated population

The 2nd stage If the process continues long enough members of

geographically and reproductively isolated populations of sexually reproducing species may become so different in genetic makeup that they cannot produce liver fertile offspring

Eventually one species has become two and speciation has occurred

Extinction is forever Extinction: process in which an entire species cease

(biological extinction) or a population of a species becomes extinct over a large region but not globally (local extinction)

Endemic species: and are specially vulnerable to extinction. Exists on islands/tropical rainforest

All species eventually become extinct 25-95% of all species are wiped out worldwide in a few

million years or less.

Section 4.5What is Species Diversity and why is it important

Species diversity includes the Variety and Abundance of species in a Particular Place Species diversity: or the number and variety of species it

contains Important component: of species diversity is species

richness: the number of different species present. Species evenness is another component: the comparative

numbers of individuals in each species are the higher is the species evenness in that community Tropical forest have high species evenness

Species-Rich Ecosystems Tend to Be Productive and Sustainable The more diverse and ecosystem is the more productive it

will be. Greater species richness and productivity will make an

ecosystem more stable or sustainable.

Species Richness and Productivity It can provide insurance against catastrophes. Species-rich communities were also less affected by drought

and more resistant to invasions by insect species. It is debatable among scientists about how much species

richness is needed to help sustain various ecosystems.

Section 4.6What roles do species play in an ecosystem

Each Species Plays a Role in its Ecosystem Each species has a specific role to play in the ecosystems where

it is found Ecological Niche: species way to live in a community and includes

everything that affects and sunlight it needs, how much water it feeds on, what it feeds on and the temperatures it can tolerate.

Generalist: broad niches Specialists: occupy niches Environmental conditions are fair: specialists have fewer

competitions Rapidly changing environmental conditions: generalists are better

Case Study: Cockroaches: Natures Ultimate Survivor Cockroaches have out lived dinosaurs, will eat just about

anything and can go a month without eating.

Species can play five major roles within the ecosystems Niches can be classified as

Native Nonnative Indicator Keystone Foundation species

Native: species that normally live there Nonnative: does not live there

Case Study: Why are amphibians vanishing Starting in the 1980s hundreds of the worlds 6,000

amphibian species have been vanishing.

Keystone species play critical Roles in their ecosystem Keystone Species: species whose roles have a large effect

on the types and abundance of other species in an ecosystem.

Play several critical roles to help sustain an ecosystem such as Pollination Top predator species

Case Study: The America Alligator-A keystone species that Almost Went Extinct One of the most important keystone species, has outlived

dinosaurs and has no natural predators except humans which in the late 1930s started to put there life at risk.

Foundation Species Help to Form the Bases of Ecosystems Foundation Species: species play a major role in shaping

their communities by creating and enhancing their habitats so they benefit other species

Three big ideas Populations evolve when genes mutate and give some individuals

genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

Human activities are decreasing the earth’s vital biodiversity by causing the extinction of species and by disrupting habitats needed for the development of new species.

Each species plays a specific ecological role (ecological niche) in the ecosystem where it is found