Chapter 3 Evolution, Species, Interactions, and Biological Communities

ORIGINS OF LIFE 1 billion years of chemical change to form the first cells, followed by about 3.7 billion years of biological change. Figure 4-2

Biological Evolution This has led to the variety of species we find on the earth today. Figure 4-2

How Do We Know Which Organisms Lived in the Past? Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis. Figure 4-4

EVOLUTION, NATURAL SELECTION, AND ADAPTATION 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.

Natural selection and adaptation modify species –Adaptation, the acquisition of traits that allow a species to survive in its environment, is one of the most important concepts in biology. –The process of better-selected individuals passing their traits to the next generation is called natural selection Evolution Leads to Diversity

What is an adaptation? The characteristics of an organism that give it an advantage. Examples of Adaptations are: 1. Color that helps camouflage them from predators 2. Speed helping them get food before another animal 3. Camels have wide two-toed feet helping them not sink in the sand 4. Leaves being flat and large to absorb more sunlight for photosynthesis

Natural Selection and Adaptation: Leaving More Offspring With Beneficial Traits 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.

Common Myths about Evolution through Natural Selection 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 ecological niche is a species’ role and environment Habitat describes the place or set of environmental conditions in which a particular organism lives. Ecological niche, describes both the role played by a species in a biological community and the total set of environmental factors that determine a species distribution. 3-10

Niches: generalists & specialists Generalists have a broad niche, like cockroaches. Specialists have narrow niches, like giant pandas. 3-11

SPOTLIGHT Cockroaches: Nature’s Ultimate Survivors 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

Specialized Feeding Niches Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-8

Evolutionary Divergence Each species has a beak specialized to take advantage of certain types of food resource. Figure 4-9

Speciation The development of a new species is called speciation. 3-15

SPECIATION, EXTINCTION, AND BIODIVERSITY 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.

Geographic Isolation …can lead to reproductive isolation, divergence of gene pools and speciation. Figure 4-10

Extinction: Lights Out 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 species EraPeriod 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 Cambrian Ordovician Silurian Devonian Extinction Paleozoic Mesozoic Cenozoic 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 Triassic Jurassic Cretaceous Extinction QuaternaryToday

Effects of Humans on Biodiversity The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4-13

Organisms that live in the same environment are always interacting with each other. Competition is one of the main interactions between organisms. Example – If two types of fish eat the same type of plant found in area of a lake, there would be competition between them. The greatest competition usually occurs between Members of the same species Why? Because they probably share identical niches.

Why does competition result in natural selection? Only the most fit individuals live to reproduce and pass on their genes to their offspring. Predation is another relationship that occurs between organisms. What is predation? Predation is when members of one population are the food source for members of another population. Example of predator/prey relationship - A hawk and a rabbit - the hawk is the predator and the rabbit is the prey

Predation affects species relationships Consumers include herbivores, carnivores, omnivores, scavengers, detritivores, and decomposers. 3-23

Predator-Wolf Prey-Moose

Some adaptations help avoid predation Toxic chemicals, body armor, extraordinary speed, and the ability to hide are a few strategies organisms use to protect themselves. 3-25

What is symbiosis? Relationships between organisms where each partner can either help, harm, or have no effect on the other partner. What is a parasite/host relationship? A parasite lives on or in another organism that it uses for food and, sometimes, for shelter. The organism the parasite uses is called the host. One organism is helped while the other is harmed. Example of parasite/host relationship- A human and a tapeworm

Tapeworm Leech

Coevolution The response of predator to prey and vice versa, over tens of thousands of years, produces physical and behavioral changes in a process known as coevolution. Coevolution can be mutually beneficial: many plants and pollinators have forms and behaviors that benefit each other. A classic case is that of fruit bats, which pollinate and disperse seeds of fruit-bearing tropical plants. 3-28

Prey Defense Mechanisms: Batesian & Mullerian mimicry 3-29

Prey Defense Mechanisms: Camouflage 3-30

Types of Symbiosis: Intimate relations among species Commensalism is a type of symbiosis in which one member clearly benefits and the other apparently is neither benefited nor harmed. Mutualism is a type of symbiosis in which both members clearly benefit. 3-31

Another example of parasitism – These butterflies spend most of their larval stage inside ant nest eating ant larvae. The butterflies are dependent on the ants and have developed ways to trick the ants into looking after them even though it is against the ants own interests to do so.

What is the difference between predator/prey relationships and parasite/host relationships? In predator/prey, the prey is usually killed right away. In parasite/host, the host organism usually lives, but is harmed. What is commensalism? A type of symbiotic relationship where one organism benefits while the other organism remains unaffected.

An example of commensalism is a clown fish (also called anemone fish) and a sea anemone. The anemone has tentacles that sting and the fish lives within these to stay protected. The anemone fish has a protective layer that prevents it form being stung.

What is mutualism? A type of symbiotic relationship where both organisms benefit. Example – Fungus growing ants feed materials to the fungus that live in their nests. The ants then feed on nutrients produced by the fungus.

What are some factors that affect population growth? Number of individuals, amount of food, space, jobs, water……. What is population density? The number of individuals in a given area

Limits to population size Density-dependent, meaning as population size increases, the effect intensifies. With a larger population, there is an increased risk that disease or parasites will spread, or that predators will be attracted to the area. Density-independent limits to population are often nonbiological, capricious acts of nature. A population is affected no matter what its size. 3-37

Low Density Small number of individuals Enough food Enough space Results in birth rate increasing and death rate decreasing This results in the density of the population increasing High Density Many individuals Little food Little space Results in death rate increasing and birth rate decreasing This results in the density of the population decreasing

Low Density High Density Xx X X x x xxxxxxxxxXxxxxx Xxxxx xxxxx Xxxxxxxxxxxxxx Xxxx xxxxxxxxx Xxxxxxxxxxxx Xxxxxxxxxxxxxxx Xxx xxxxxxxxxx Xxxxxxxxxxxxxx Xxx xxx xxxxxx

What is carrying capacity? The size of a population that can be supported by any ecosystem What is zero growth? The population size is no longer increasing – the birth rate and the death rate are about equal

S curve of logistic growth 3-41

3.4 Properties of Communities Depend on Species Diversity Diversity and abundance –Diversity is the number of different species per unit area. –Abundance refers to the number of individuals of a species in an area. 3-42

Species patterns create community structure Boundaries of species populations and communities form patterns that fit together: –(1) individuals and species are spaced throughout communities in different ways; –(2) the communities themselves are arranged over a large geographic area or landscape –(3) communities have relatively uniform interiors (“cores”) and also “edges” that meet. Community (or ecological) structure refers to these patterns of spatial distribution of individuals, species, and communities. 3-43

Individuals in communities are distributed in various ways Random patterns arise from random distribution of resources. Uniform patterns usually arise from competition. Cluster patterns help a species protect themselves. 3-44

3.5 Communities Are Dynamic and Change Over Time Climax community-The community that developed last and lasted the longest. Primary succession- land that is bare of soil—a sandbar, mudslide, rock face, volcanic flow—is colonized by living organisms where none lived before. Secondary succession-after a disturbance, if left undisturbed, a community will mature to a characteristic set of organisms. Pioneer species-the first species to colonize a community in primary succession on land. 3-45