Species Classification and Macroevolution

Macroevolution Macroevolution is evolution on a large scale. Changes we can see visibly as species evolve slowly over a long period of time.

Carolus Linnaeus: ( ) Swedish naturalist, created the first classification of all living creatures. –Taxonomy –Species –Genus Classifying Species

Linnaean Taxonomy

Kingdom Kingdom: the most inclusive category. All living organisms can be put into 1 of 5 kingdoms. –Plants –Animals –Fungi –Single-celled organisms –Bacteria

Kingdom The major differences between the 5 kingdoms are their mobility and their sources of food. –Example: Plants have to produce their own food while animals must acquire and ingest food.

Phylum The kingdom Animalia contains about 35 phyla. Humans belong to the phylum Chordata. –Chordata is a vertebrate phylum; animals which possessed at one point in their life a notochord. A notochord is a flexible rod that runs along the back of the animal.

Phylum Humans belong to the subphylum Vertebrata, which means animals with a vertebral column (a backbone) One characteristic of vertebrates is bilateral symmetry. Most vertebrates also have the same basic skeletal structure. –Example: a single upper arm bone and two lower arm bones

Class There are 7 classes within the phylum Chordata. Humans belong to the class Mammalia. Mammals evolved from reptiles, more than 200 million years ago.

Order Humans belong in the order Primates, which includes apes, monkeys, and prosimians.

Family and Genus Humans belong to the Hominid family, the great apes, which include humans, gorillas, orangutans, and chimpanzees. Genus: humans belong to the genus Homo which includes all modern humans and species (now extinct) which were closely related.

What is a Species? What determines how we classify species? Two schools of thought: –Biological Species Concept –Ecological Species Concept

What is a Species? The Biological Species Concept: –Is defined as a group of organisms that interbreed. –Reproductive isolation states that members of one group cannot successfully breed with members outside that group. –The ability to breed leads to gene flow in the population. –(Humans belong to the species Sapiens, this includes all modern humans.)

What is a Species? Ecological Species Concept: –Critics of the BSC point out that gene flow is not necessary nor sufficient to maintain species boundaries in every case. –Natural selection plays an important role in preserving the boundaries between species.

What is a species? Can interbreed naturally. Are reproductively isolated from other species. Must produce fertile offspring. (Genus: one level up from species)

Intraspecific: refers to variation seen within the same species. Interspecific: refers to variation beyond that seen within the same species to include additional aspects seen between two different species.

Subspecies Groupings of species that are physically distinct from one another but are still capable of interbreeding. Example: Papio cynocephalus cynocephalus, is 1 of 3 species of the yellow baboon.

Reproductive Isolating Mechanisms The genetic isolation of a species which causes them to be unable to produce fertile offspring. Opposite of gene flow.

Reproductive Isolating Mechanisms Behaviors (seasonal or diurnal/nocturnal)

Reproductive Isolating Mechanisms Geographical Ecological

Reproductive Isolating Mechanisms Mechanical Sexual “courtship” behaviors

Reproductive Isolating Mechanisms Hybrid inviability Hybrid sterility

How species change Speciation: new species from a “parent” species. Gradual change. Anagenesis. Cladogenesis.

How species change Anagenesis: –“Straight-line” evolution. –Species can gradually change over time until the accumulation of changes becomes so great that we label it as a different species.

How Species Change Cladogenesis: –One or more new species from another gradually over time. –Process begins with one species and ends with multiple species due to branching.

Speciation Speciation: new species from a “parent” species. Reduction of gene flow followed by genetic divergence such as mutation or natural selection. At minimum outcome is two separate species, but sometimes many new species can form which is the result of adaptive radiation.

300 closely related cichlids species found nowhere else. DNA studies show that they arose from a single ancestral species.

Speciation Allopatric Speciation: –When a population is divided by a barrier, different parts of the population adapt to different environments

Speciation Allopatric speciation: –The longer the groups remain isolated the greater the genetic difference is between the groups. –When the separation results in complete reproductive isolation, a new species is formed. –Requires a physical barrier that interrupts gene flow and allows the two populations to divergence by means of natural selection.

Speciation Parapatric speciation: –A new species can be formed if selection is combined with partial genetic isolation. –At habitat boundaries, a hybrid zone can be formed. Hybrid zones are created at the boundaries of habitats, but hybrids are not favored by selection.

Speciation Sympatric speciation: –Speciation can occur even in the absence of a physical barrier. –Adaptive radiation occurs when a single species diversifies to fill numerous ecological niches.

Adaptive Radiation Is the result of new environments or a series of adaptations. With the right ecological opportunities a group of related species can spread into a number of niches.

Adaptive Radiation 1. When an environment doesn’t have a similar or competing species. 2. When a large extinction rids a set of environments of competing species. 3. When the new group of related species are adaptively generalized (rather than specialized) and are able to disperse successfully into niches and displaces species already there.

Adaptive Radiation

Gradualism: evolutionary changes are slow but steady over time. Punctuated Equilibrium: gradualism punctuated with relatively short spurts of rapid evolutionary change.

Extinction It has been estimated that 99% of all species that have ever existed have become extinct. Mass extinction: many species becoming extinct at the same time. Can result in punctuated equilibrium.

Common Misconceptions of Evolution That it has directionality. Bigger = better. Natural Selection ALWAYS works.

Taxonomy: describing and classifying organisms. –Linnaeus used traits to group organisms. Example: Mammals: all breath oxygen, have hair and mammary glands, and three middle ear bones.

Classifying Species Terms used in classification: –Homology: classifying based on similarities with a common ancestor. Typically based on the structure of species.

Classifying Species Homoplasy: evolutionary traits which are independent but similar. There are two types of homoplasy: –Convergent evolution –Parallel evolution

Classifying Species Convergent Evolution: independent evolution of similar traits (for example birds and flies both have wings). Parallel evolution: evolution of similar traits in closely related species (such as increase in dental size in early human ancestors)

Primitive and Derived Traits Primitive trait: a trait which has not been altered from an ancestral state. Example: Fossil evidence shows that the first mammals had five digits, so the fact that humans have five fingers and toes is a primitive trait.

Primitive and Derived Traits Derived trait: a trait which has been altered from an earlier form. –Horses have hooves, so because early mammals had five digits, a horse’s hoof would be considered a derived trait.

Primitive and Derived Traits What is considered a primitive or derived trait is relative.

Classification Two major schools of thought: –Evolutionary Systematics: stresses the similarities of all homologous traits (primitive or derived) when classifying organisms into groups. –Cladistics: stresses evolutionary relationships between organisms based on shared derived traits.

Classification Evolutionary Systematics: –Think of a family tree. –First started by paleontologists in the 19 th century.

Classification Cladistics: –Provides an explicit and testable hypothesis of organisms’ relationships. –Members of a group share a common evolutionary history, and are "closely related," more so to members of the same group than to other organisms. –The most commonly used method to classify organisms.

Fossils Formed through a process called mineralization. This happens slowly as water, carrying minerals, seeps into the small spaces within bone. Traces of life forms that include insects trapped in tree sap, leaf imprints, footprints, skeletal remains.

Fossils Amber: fossilized tree sap which can sometimes contain small animals such as mosquitoes

Fossils Taphonomy: is the study of how bones and other materials come to be buried in the earth and preserved as fossils.