Zoo Evolution & Taxonomy

Jean-Baptiste de Lamarck

developed an early theory of evolution based on:

1) Use & disuse: parts of the body that are used extensively become larger & stronger, while those that are not used deteriorate

2) Inheritance of acquired characteristics: characteristics acquired during an organism’s lifetime could be passed on to the next generation

*Lamarck’s explanatory mechanism was flawed*

Charles Darwin

developed natural selection as his mechanism for evolution:

-natural selection explains how adaptations arise

1) Genetic variation

2) Overproduction

3) Competition

4) Selection favors a trait

5) Evolution occurs as the unequal reproductive success of individuals leading to adaptations to their environment

6)Artificial selection

Genetic variation

Individuals in a population vary in their traits, many of which are heritable.

Overproduction

A population can produce far more offspring than can survive.

Competition

With more individuals than the environment can support, competition for resources is inevitable

Selection favors a trait

Individuals with inherited traits that are better suited to the local environment are more likely to survive and reproduce than individuals less well-suited.

Artificial selection

process by which species are modified by humans

*Individuals do NOT evolve; Populations evolve*

Example: Selective breeding for milk or meat production; development of dog breeds

Adaptations

characteristics that enhance organism’s ability to survive and reproduce in specific environments

Rapid speciation

new species filling new niches, because they inherited successful adaptations

Speciation

If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process.

*individuals from the new population are unable to mate successfully with individuals from the parent populations*

Homology

characteristics in related species can have an underlying similarity even though they have very different functions

Homologous structures

are anatomically similar structures with similar development.

Embryonic homologies

comparison of early stages of animal development reveals many anatomical homologies in embryos that are not visible in adult organisms.

Vestigial organs

-structures of marginal, if any, importance to the organism.

-remnants of structures that served important functions in the organism’s ancestor.

Molecular homologies

shared characteristics on the molecular level

(DNA, proteins, amino acid sequences)

Homeotic genes

master regulatory genes that determine the location and organization of body parts.

Convergent evolution

taken place when two organisms developed similarities as they adapted to similar environmental challenges – not because they evolved from a common ancestor.

explains why distantly related species can resemble one another

Analogous structures

similar functions with different internal structures & development

Example: bird wing/insect wing/bat wing

Biogeography

The geographic distribution of species

1) Species in a discrete geographic area tend to be more closely related to each other than to species in distant geographic areas.

2)Continental drift and the break-up of Pangaea can explain the similarity of species on continents that are distant today.

3)Endemic species are found at that certain geographic location and nowhere else.

The biological species concept

defines a species as: a group of individuals who have the potential to interbreed in nature and produce viable, fertile offspring.

Prezygotic & postzygotic

two types of barriers that prevent members of different species from producing offspring that can also successfully reproduce.

Prezygotic barriers

prevent mating or hinder fertilization if mating has occurred, include the following:

-Habitat (geographic) isolation

-Behavior isolation

-Temporal isolation (reproductive isolation)

-Mechanical isolation

-Gametic isolation

Postzygotic barriers

prevent a hybrid zygote from developing into a fertile adult:

-Reduced hybrid viability (frail offspring)

-Reduced hybrid fertility (infertile offspring)

Sexual Reproduction

-Advantage: genetic variation

-Disadvantage: energy requirement

Asexual Reproduction

-Advantage: numerous offspring, relatively quick, little energy required to find a mate

-Disadvantage: little genetic variation

allopatric speciation

a population forms a new species because it is geographically isolated from the parent population. When the population is geographically isolated gene flow is interrupted, resulting in reproductive isolation.

-geological events or processes that can fragment a population, resulting in geographical isolation of new populations

-Small, newly isolated populations undergo allopatric speciation more frequently because they are more likely to have their gene pools significantly altered.

Sympatric speciation

small part of a population forms a new species without being geographically separated from the parent population.

-population switching to a new habitat

-switching to a different resource such as food

-an accident during cell division, resulting in extra sets of chromosomes (polyploidy)

Adaptive radiations

periods of evolutionary change in which: groups of organisms form many new species whose adaptations allow them to fill open ecological niches.

Gradualism

proposes that species descended from a common ancestor and gradually diverge more and more in morphology as they acquire unique adaptations

Punctuated equilibrium

term used to describe periods of apparent stasis punctuated by sudden change observed in the fossil record

Carolus Linnaeus

-Grouped similar species into increasingly general categories based on a set of characteristics used to assess similarities and differences

-Developed taxonomy

-Developed binomial nomenclature

Taxonomy

branch of biology dedicated to the naming & classifying of all forms of life

-Hierarchical categories: Kingdom, Phylum, Class, Order, Family, Genus, Species (King-Phillip-Cried-Out-For-Goodness-Sake)

binomial nomenclature

two-part Latin naming system that includes the organism’s genus and species

Genus species

Example: leopard Panthera pardus

Dichotomous Key

*dichotomy means “two opposite parts or categories”*

-chooses between a series of two opposite statements that best describes the organism, until the user reaches the organism’s name

-should NOT use vague descriptions

- should only identify one characteristic

Phylogenetic Trees (dendograms)

-display the passage of time on the vertical axis and the degree of evolutionary divergence on the horizontal axis.

-shows the relationship between organisms based on their characteristics, genetic background, & evolutionary relationships.

-Estimating degree of evolutionary connection

1) Base of phylogenetic tree represents the ancestral species with primitive character(s)

2) Branches farther from the base of the tree, represent progressively more recent evolutionary lines & degree of relationship between species is based on the percentage of shared derived characters

3) Groups are organized based on the sequence in which unique derive characters appear in members of the related group -- Taxa on the same phylogenetic branch are closely related

Cladogram

shows relationship of shared anatomical features-shows the relationship of the closely related organisms

-made by compiling data on homologous characteristics shared by species

-can NOT show evolutionary links but they depict patterns of shared characteristics

Asymmetrical

no symmetry

Radial symmetry

parts in a circular arrangement around an axis

Bilateral symmetry

two similar halves on one central axis (animal tends to exhibit cephalization)

-Dorsal (back)

-Ventral (abdomen)

-Anterior (toward front/head area)

-Posterior (toward tail end)

Dorsal

back

Ventral

abdomen

Anterior

toward front/head area

Posterior

toward tail end

Types of Body Cavities

-Acoelomate

-Pseudocoelom

-Coelom

Acoelomate

-no body cavity

-interior of animal is solid except for digestive tract/cavity

Pseudocoelom

-body cavity is NOT completely lined with mesoderm

-mesoderm does NOT surround the exterior of the endodermic gut

Coelom

-cavity completely lined with mesoderm

-surrounds and supports the endodermic gut