Understanding Biodiversity and Evolution

• Biodiversity refers to the number of different species in an ecosystem.
• Measures of biodiversity also need to consider the relative population sizes of different species to be accurate.
• Types and levels of biodiversity are important to consider when studying biodiversity.
• Species richness and evenness are also crucial measures of factors in biodiversity.
• Understanding the values and importance of biodiversity is essential.
• Recognizing threats to biodiversity is an important element of studying biodiversity.
• Functional redundancy and keystone species play a vital role in biodiversity.
• Biodiversity hotspots need to be recognized and protected.
• Earth's impressive biodiversity is the result of millions of years of evolution.

Evolution

• Evolution is defined as a change in a population's genetic makeup over time.
• Populations, not individual organisms, evolve by becoming genetically different.
• The theory of evolution is based on the idea that all species are related and gradually change over time.
• Evolution relies on genetic variation within a population, affecting an organism's phenotype.
• Traits that provide an advantage can be passed on to offspring.

Four Theories on Evolution

• Variation exists within every species, even among related individuals.
• Siblings can vary in color, height, weight, and other characteristics.
• Certain characteristics, like the number of limbs or eyes, rarely vary.
• Each species possesses traits determined by inheritance.
• Characteristics of offspring are determined by inherited traits passed from parents.
• Traits that improve survival odds are more likely to be passed on.
• Some characteristics like weight and muscle mass can be affected by environmental factors, such as food availability.
• Most species produce more offspring than the environment can support; Competition results from limited natural resources.
• The struggle for resources determines the mortality rate within a species. Surviving individuals breed and pass on their genes.

Survival of the Fittest

• Some individuals survive the struggle for resources and reproduce, adding their genes to future generations.
• Traits aiding survival are passed on to offspring, demonstrating natural selection.
• Environmental conditions lead to the survival of individuals with specific traits passed through heredity.
• Individuals of a species are not identical and traits are passed to each generation.
• More offspring are born than the environment can support, so only the competition survivors reproduce.

Evolution Also Includes

• Populations have the potential to increase exponentially.
• Populations generally remain stable after reaching a certain size due to limited natural resources.
• Individuals in a population vary, and some characteristics are heritable.
• Not all offspring survive and reproduce due to a struggle for resources.
• Some individuals are more likely to survive and reproduce because of their heritable traits.
• Differences in survival and reproduction are non-random, with some traits passed on at a higher rate. This results in evolution by natural selection.

Two Forms of Evolution

• Microevolution involves small genetic changes within a population.
• Macroevolution involves long-term, large-scale evolutionary changes, like speciation and extinction.

Microevolution

• Microevolution is evolutionary change within a species or small group of organisms over a short period and may not be visible to casual observers. Examples include pesticide and herbicide resistance.

Causes Of Microevolution

• Mutation: random changes in the structure/number of DNA molecules in a cell; often seen as the ultimate source of genetic variability.
• Natural selection: some individuals of a population have genetically based traits that cause them to survive & produce more offspring than others.
• Gene flow: the movement of genes between populations; can change the genetic composition of local populations.
• Genetic drift: changes in the genetic composition of a population by chance; especially important for small populations.

Consequences of Evolution

• Adaptation: populations become better suited to their environments through the accumulation of advantageous traits.
• Speciation: given enough time and sustained, populations can diverge sufficiently to become distinct species, a process is known this.
• Biodiversity: contributes to the diversity of life forms within a given habitat by promoting genetic variation and adaptation.

Macroevolution

• Macroevolution refers to large-scale evolutionary changes over geologic time leading to new species. It results from microevolution.
• Included are novel life forms, species extinction, and the mechanisms driving diversity.
• Macroevolutionary patterns include mass extinctions, adaptive radiation, convergent evolution, coevolution, punctuated equilibrium, and developmental gene changes.

Mass Extinctions

• Extinction constantly occurs and mass Extinctions wipe out ecosystems.
• Mass Extinctions disrupt energy flow and collapse food webs.
• Causes of Mass Extinctions include volcanic or geologic activity.
• Habitats left unoccupied after extinction provide ecological opportunity.
• Evolution explosions occur and there are ecological opportunities making new habitats available.
• Rapid evolution results in many new species.

Adaptive Radiation

• A single species or small group of species evolve into several different forms that live in different ways.
• Examples include Darwin's Finches and Cichlid fish in Lakes Victoria & Malawi.

Convergent Evolution

• Convergent evolution occurs when species occupy similar ecological niches and adapt in similar ways in response to similar selective pressures.
• Bats and birds, different creatures, evolved the ability to fly.

Coevolution

• Coevolution is the process by which two species evolve as they interact with one another.
• This involves plants and herbivores evolving alongside each other.

Punctuated Equilibrium

• Evolution occurs in spurts rather than a slow, steady path.
• Long periods of stasis with little activity in terms of extinctions or new species are interrupted by intermittent bursts of activity.

Patterns of Evolution

• Mass extinctions: dinosaurs.
• Adaptive radiation: species evolved into several different forms that live in different ways.
• Convergent evolution: unrelated organisms come to resemble one another.
• Coevolution: the process by which two species evolve in response to changes in each other over time.
• Punctuated equilibrium: patterns of long, stable periods are interrupted by brief periods of more rapid change
• Gradualism: patterns of slow, gradual change.

Importance of Macroevolution

• Macroevolution drives diversification of life forms, leading to new species adapting to environments and evolving unique traits, that lead to biodiversity across ecosystems.
• It provides insights into evolutionary change driving processes across broader spatial and temporal scales.
• Changes in species composition and diversity can affect nutrient cycling, energy flow, and resilience, thus impacting the stability and functioning of ecosystems.
• Through the processes of dispersal, vicariance, and adaptive radiation, species colonize new regions, diversify in isolated habitats, and contribute to broader biodiversity gradients.

Natural Selection

• Natural Selection is a process where a particular beneficial trait is reproduced in succeeding generations more than other traits.
• It is the process through which populations of living organisms adapt and change.
• Individual organisms that happen to be best suited to an environment survive and reproduce more successfully, producing many well-adapted descendants.
• After numerous breeding cycles, the better-adapted dominate.
• Nature has filtered out poorly suited individuals, and the population has evolved.

Natural Selection Observations

• Variation is observed in every species population.
• Some species population members will have beneficial variations ensuring better survival.
• The members of a population with the beneficial variations will leave the most offspring.
• The beneficial traits are heritable & passed to future generations.

Evolution by Natural Selection

• The struggle for species existence as each competes for food, shelter, and other life necessities.
• Survival of the fittest as some individuals are better suited to the environment.

Natural Selection Characteristics

• Variation: Organisms (within populations) exhibit individual variation in appearance and behavior, involving body size, hair color, and number of offspring.
• Inheritance: Some traits are consistently passed on from parent to offspring
• Heritable traits are strongly influences by environmental conditions and show weak heritability.
• High Rate of Population Growth: Most populations have more offspring than local resources can support, leading to a struggle for resources; each generation experiences substantial mortality.
• Differential Survival and Reproduction: Individuals possessing traits well suited for the struggle for local resources will contribute more offspring to the next generation.

Variation & Heritability

• A giraffe's long neck is an adaptation that helps the giraffe survive in its environment.
• A species doesn't know what traits will be advantageous in the future, and genetics is pure.
• If a trait is advantageous and helps the individual to survive and reproduce, the genetic variation is more likely to be passed to the next generation, which equals heritability.

Artificial Selection

• Artificial Selection is the evolutionary process in which humans consciously select for or against particular features in organisms.
• For example, by choosing which individuals to save seeds from or breed from one generation to the next.

Artificial Selection Process

• The Artificial selection process occurs under human direction.
• Breeders create the great variety of dog breeds and crop plants by breeding animals with particular features.

Importance of Artificial Selection

• Artificial selection can create crops with a higher yield and a shorter harvest time.
• Crops with higher resistance to pests and diseases may also be selectively bred.
• Reduced costs occur because farmers can identify crops or animals from their resources to be used.
• It can create new plant and animal varieties.

Adaptations

• An adaptation is a feature that arose and was favored by natural selection for its current function, helping an organism survive or reproduce.
• Structural: coloration, mimicry, protective, gripping.
• Physiological: hibernate, chemical.
• Behavioral: ability to fly, migrate.

Limits to Adaptation

• Environmental changes lead to adaptation only for traits already in a population's gene pool.
• Adaptations are usually compromises because each organism does many things.
• A population's reproductive capacity can limit its ability to adapt even with a beneficial heritable trait.
• A favorable genetic trait can only predominate if most individuals with other traits die or become sterile.

How New Species Evolve

• Speciation: one species splits into two or more species adapt to an ever-changing environment.
• Allopatric speciation: depends on geographic isolation to happen first; physical isolation of populations for a long time.
• Reproductive isolation: a species' inability to breed successfully with related species due to barriers.

Importance of Evolution

• Evolution explains biodiversity and accounts for similarities and differences among species through mechanisms like natural selection, genetic drift, and gene flow.
• It is crucial for survival, so all living things must be able to adapt to be able to adapt to their surroundings or perish.
• Explains how life developed on Earth and how different species are connected, guiding conservation efforts.
• Evolutionary theory explains how organisms adapt to their environments over time.
• Evolutionary linkages help address biological challenges and understand the diversity of life.

Types of Extinctions

• Biological Extinction: No species member alive.
• Background Extinction: the number of species is based on (non-human) factors.
• Extinction Rate: percentage or number of species that go extinct over a time period..

Extinction Classification

• Mass extinction: many species go extinct over a short period due to major events from global changes in environmental conditions.
• Background extinction: the number of species expected to go extinct are not caused by major events over a period of time.

Levels of Species Extinction

• Local extinction: the termination of a species in a chosen geographic study area.
• Biological: species complete disappearance from Earth.

Factors Leading to Extinction

• Plate tectonics
• Climatic changes over time
• Natural catastrophes
• Human impacts

Extinction Risks

• Specialization and resource partitioning increasing diversity.
• Tradeoff is that organisms can become more vulnerable to extinction.

Localized Distribution

• Competition with other populations is avoided by living in a limited area.
• The risk is that a natural disaster will destroy the limited habitat.

Overspecialization

• Competition with other species are reduced when Organisms have specialized feeding habits.
• If the food source is limited and goes extinct, so does the species feeding on it.

Interactions

• Competition and predation are reduced by species isolation.
• Introduced new predators or competitors may threaten the survival of an isolated species.

Habitat Loss

• Habitat loss is the greatest cause of extinction.
• Organisms with highly specialized habitat needs may avoid competition, but risk extinction if their habitat is threatened.
• Tropical rainforests are currently logged at a high rate, mostly for grazing cattle and cultivation