[BIO23] Lecture Exam Reviewer (book of Ching only)

Organic evolution

• defined as change in genetics of a population over time or generations

• can be studied in two different levels:

  • Microevolution

  • Macroevolution

Population

all individuals of the same species living in a defined area at the same time

same species, same place, same time

Microevolution

small-scale genetic changes within populations

• occurs through several mechanisms

• example: natural selection

Natural Selection

• evolution that occurs because individuals with some traits survive and reproduce better than do individuals with other traits

• process by which individuals with advantageous traits are more likely to survive and reproduce. Over time, these traits are passed on at a higher rate, making them more common in the population.

Fitness

degree to which individuals with certain traits are expected to survive and reproduce

Adaptation

refers to either the process of natural selection or to a trait that has evolved through natural selection

Darwin’s Four Postulates

1. Variation – Individuals in a population are different from one another.

2. Genetic differences - The differences among individuals are based on genetics.

3. Overproduction – More offspring are produced than can survive.

4. Differential survival and reproduction – Individuals with traits that help them survive and reproduce are more likely to pass those traits on.

Results of the Four Postulates

• those individuals with higher fitness get to survive and reproduce more

• since traits are genetic, they get passed on and become more common

Macroevolution

large-scale results of genetic changes in populations

• example: formation of new species, evolution of large-scale trends seen across species in what traits they have

Speciation

• refers to the formation of new species

• occurs when one ancestral species evolves into more than one descendant species

Species

groups of organisms that are so similar to each other that they can reproduce and produce healthy fertile offspring

Phylogeny

• evolutionary history of species, or history of speciation

• evolutionary relationships among species or to the family tree of all life, indicating how all living things are related

• typically diagrammed as a tree

What does the history of speciation tell us?

1. if they are close relatives, meaning they evolved to be separate species relatively recently

2. if they are distant relatives, meaning they evolved to be separate species long ago

Primitive Traits

• also called plesiomorphic characters

• characteristics of organisms that were present in the ancestor of a certain group of related organisms

Derived Traits

• also called apomorphic characters

• characteristics of organisms that have evolved within the group or related organisms that were not present in the ancestor

Synapomorphy

character is present in the immediate common ancestor but not in the earlier ancestor

Symplesiomorphy

character present in the immediate common ancestor and the earlier ancestor

Homology

similarity from a common ancestor

example: arm bones of humans, wing bones of bats, and flipper bones of whales are similar because they descended from a common ancestor

Analogy

similar function but different origin

example: bird wings and insect wings (same function but due to ancestry, i.e. could be adaptation or evolution)

Homoplasy

similar trait without common ancestor

example: bird wings and insect wings (due to convergent evolution)

Coelomates

animals with fluid-filled internal body cavity (coelom)

2 Evolutionary Lines of Coelomates

1. Protostomes

2. Deuterostomes

Protostomes

• first mouth

• coelomates whose mouth forms from or near the embryonic blastopore

• example: mollusks, annelids, arthropods

Deuterostomes

• second mouth

• coelomates whose anus forms from or near the embryonic blastopore

• mouth forms at the opposite end of the embryo

• examples: echinoderms, protochordates, chordates

Why are chordates grouped with deuterostomes?

• mouth forms opposite to the blastopore

• cleavage is generally radial

• coelom is enterocoelom

• skeleton arises from the mesoderm

Subphyla in Phylum Chordata

1. Cephalochordata (amphioxus)

2. Urochordata (tunicates)

3. Vertebrata (vertebrates)

invertebrates: tunicates and amphioxus

Differences in the Three Chordate Subphyla

1. Cephalochordates and urochordates are all marine animals, and lack a bony or catilaginous skeleton. They are suspension feeders.

2. Most vertebrates have endoskeleton and some are terrestrial and most use jaws to feed.

Similarities in the Three Chordate Subphyla

they share a common body design similar in four basic features:

1. notochord

2. pharyngeal slits

3. dorsal hollow nerve cord

4. postanal tail

Notochord

• slender rod that arises from the dorsal wall of the embryonic gut in primitive chordates

• lies above the coelom and is axially incompressible but laterally flexible

• typically composed of a core of cells and fluid encased in a tough sheath of fibrous tissue

• in vertebrates, it is replaced by the vertebral column

• in adult mammals, it is reduced to as remnant known as the nucleus pulposus

Pharyngeal Slits

• also known as pharyngotremy

• elongated openings in the lateral wall of the pharynx

• part of the digestive tract located immediately posterior to the mouth

Dorsal Hollow Nerve Cord

• hollow canal surrounding the neurocoel

• tubular in structure

• fluid-filled central canal

Postanal tail

• represents posterior elongation of the body extending beyond the anus

• an extension of the chordate locomotor organ, the segmental musculature and notochord

Chordate Classification

• occupy a wide variety of marine, freshwater, and terrestrial habitats

• notochord, pharyngeal gill slits, dorsal tubular nerve chord, and a postanal tail are present at some time

Two Groups of Chordates

1. Protochordates

2. Craniates

Subphyla under Protochordata

1. Urochordata

2. Cephalochordata

Classes under Subphylum Urochordata

TAAS

1. Thaliacea

2. Ascidiacea

3. Appendicularia

4. Sorberacea

Subphylum Urochordata

oura - tail, chorda - cord

characterized by:

• Tunicata: sea squirts or tunicates

• notochord, nerve cord, and postanal tail present only in free-swimming larvae

• Ascidian adults sessile (immobile), occasionally planktonic, encased in tunic that contains some cellulose, marine

Class Ascidiacea

• all sessile (immobile) as adults

• solitary or colonial

• colony members interconnected by stolons

• sea squirts

Class Appendicularia (Larvacea)

• planktonic

• adults retain tail and notochord

• lack a cellulose tunic

• epithelium secretes a gelatinous covering of the body

Class Sorberacea

• ascidian-like urochordates possessing dorsal nerve cords as adults

• deep water

• benthic (lowest level, bottom)

• carnivorous

• Octanemus sp.

Class Thaliacea

• planktonic

• adults are tailess and barrel-shaped

• oral and atrial openings are at opposite ends of the tunicate

• water current produced by muscular contraction of the body wall

Subphylum Cephalochordata

kephale - head, chorda - cord

• Branchiostoma sp.: lancelets (amphioxus), Assymetron sp.

• notochord, nerve cord, postanal tail and gill slits persist throughout life

• body laterally compressed and transparent

• fishlike in form

Subphylum under Group Craniata

Subphylum Vertebrata

Superclasses under Subphylum Vertebrata

1. Superclass Agnatha

2. Superclass Gnathostomata

Superclass Agnatha

• without jaws

• includes Cyclostoma or cyclostomes (“circle mouth”, jawless vertebrates): hagfishes and lampreys

• without true jaws and appendages

Classes under Superclass Agnatha

1. Class Myxini

2. Class Cephalaspidomorphi

Class Myxini

• fish-like

• jawless

• no paired appendages

• terminal mouth with 4 pairs of tentacles

• nasal sac with duct to pharynx

• 5 - 15 pairs of gill slits

• Hagfishes

Class Cephalaspidomorphi

• fish-like

• jawless

• no paired appendages

• suctorial mouth with horny teeth and rasping tongue

• nasal sac not connected to mouth

• 7 pairs of gill slits

• Lampreys

Superclass Gnasthomata

• gnathos - jaw, stoma - mouth

• includes jawed fishes and all tetrapods (four leg-like appendages)

• usually has paired appendages

Classes under Superclass Gnasthomata

COARAM

1. Class Chondrichthyes

2. Class Osteichthyes (Teleostomi)

3. Class Amphibia

4. Class Reptila

5. Class Aves

6. Class Mammalia

Class Chondrichthyes

• chondros - cartilage, ichthys - fish

• streamlined fish-like body with heterocercal tail

  • heterocercal - different lobe sizes of tail

• paired appendages

• cartilaginous skeleton

• 5 - 7 gills with separate openings

• no operculum

• no swim bladder

simpler terms, they are cartilaginous fishes

Class Osteichthyes (Teleostomi)

• osteon - bone, ichthys - fish

• primitively fusiform body, but variously modified

  • primitive fusiform means torpedo or spindle-like body

• mostly ossified skeleton

• single gill opening on each side (covered by operculum)

• with swim bladder

• bony fishes

Classes under Class Osteichthyes

1. Class Sarcopterygii (lobe-finned fishes)

2. Class Actinopterygii (ray-finned fishes)

Class Amphibia

• amphi - both/double, bios - life

• ectothermic tetrapods

  • ectothermic means that they rely on the external environment to regulate their internal body temperature

• respiration by lungs, skin, or gills

• skin moist with mucous glands

• lack scales

• aquatic embryonic developmental stages, followed by metamorphosis to an adult

• Frogs, toads, newts, salamanders

Class Reptilia

• repere - to creep

• ectothermic tetrapods

  • rely on external environment to regulate their internal body temperature

• dry skin

• lack mucous glands

• covered by epidermal scales

• terrestrial embryonic developmental stages

• no larval stage

• amniotic eggs

• Turtles, snakes, lizards, alligators

Class Aves

• aves - birds

• endothermic vertebrates

  • uses own energy to regulate their internal body temperature

• modified front limbs → wings (for flight)

• feather-covered body

• scales on feet

• amniotic eggs

Class Mammalia

• mamma - breast

• endothermic vertebrates

  • uses own energy to regulate internal body temperature

• partially covered with hair

• well-developed brain

• young nursed from mammary glands

• mammals