Lesson 1: Introduction to Comparative Vertebrate Anatomy

Comparative Vertebrate Anatomy

The study of vertebrate structures, functions, development, and evolution through comparison.

Phylogeny

The study of evolutionary relationships and ancestry among vertebrates

Homology

Similarity of structures due to a shared evolutionary ancestor.

Analogy

Similarity of function in structures with different evolutionary origins

Homoplasy

Similar traits that evolved independently in different species.

Form and Function

The relationship between a structure’s shape and its function.

Evolution

The gradual change of vertebrate species over time.

Vestigial or Rudimentary Structures

Reduced structures that remain from ancestral forms.

Ontogeny

The development of an organism from embryo to adulthood.

Heterochrony

Changes in the timing of developmental processes.

Comparative Vertebrate Anatomy

• A study of vertebrate structure, function, and evolution.

• Relationships between the structural and functional adaptations of the different vertebrate groups and their environment are examined.

• This is a comparative study of the nine major organ systems found in vertebrate animals, with considerations of human systems.

• Evolutionary and functional aspects of anatomical differences among vertebrate groups are emphasized.

• Integumentary, Skeletal, Muscular, Cardiovascular/Circulatory, Respiratory, Digestive, Urinary/Excretory, Reproductive System

Anatomy

• is the study of the body parts of an organism and how they are arranged.

• body parts and location

Morphology

is the study of the shape, form, and structure of body parts.

Notochord, dorsal hollow nerve chord, pharyngeal slits, and post-anal tail

Every vertebrate has:

Notochord

• A soft, rod-like part inside the body.

• It supports the body and helps it keep its shape.

• It later becomes the backbone in many animals

• ____ in human (embryonic stage) gets bigger as we age (backbone/spine)

• neck to tail (other vertebrates)

• neck to waist (humans)

• Function: Main support

Dorsal Hollow Nerve Cord

• A long, hollow tube found along the back.

• It connects the brain to the rest of the body

• It sends messages to different parts of the body.

• It controls movement and body actions.

• Brain → hollow nerve cord → nerves ending

Pharyngeal Slits

• Small openings in the throat area

• They help some animals breathe in water (for eating - exit the water while feeding)

• In humans, they develop into parts of the ear and throat. (until embryonic stage - it become part of the ear and throat)

Post-Anal Tail

• A tail located after the anus.

• It helps with movement and balance.

• Some animals keep it, while others lose it as they grow.

• Humans - tailbone

• Function (terrestrial vertebrates): courting, balance, signaling

Vertebral column or backbone

• surrounds and protects the spinal cord (neck to waist)

• Made of a series of bones called vertebra or vertebrae

• Function: Stiffening of the body, attachment site for muscles, attachment site for pectoral and pelvic girdle, protects and supports the spinal cord

Vertebra or vertebrae

Vertebral column is made of a series of bones called

Centrum

The vertebrae has two main parts

_____ - Structural support and weight-bearing capacity

• Attaches or connects vertebra to another

• protects the spinal cord by maintaining strength and stability of vertebral column

• bony-disk shaped flat and round

Vertebral arch/Neural arch

• attachment site for muscles and ligaments involved in movement and posture.

• Bony structure of vertebra

• Forms the dorsal (back)

• part of vertebrates

• also protects and supports the spinal cord

Phylogeny

• study of evolutionary relationships/ history of a group or structure.

• common ancestry

• understand evolutionary branching

• relationships of vertebrates groups

Paleontology, Functional Adaptation or Comparative Morphology, Embryology

Three ways to study Phylogeny

Vertebrate Paleontology

• The study of the fossil record of the history of animals with backbones and is termed

• Identification, Classification and Analysis of vertebrate fossils

Functional adaptation

• includes the evolutionary modification or changes in the body and how the body works that help an organism survive and reproduce in their environment

• Example: The giraffe's neck, which can grow to as much as 2 meters in length, has been selected because it gives its owner exclusive access to the topmost leaves of the trees, and no other animal can reach them.

Embryology

is the study of how embryos grow, from the moment of fertilization until basic body parts and organs form. It helps us understand how genes and the environment affect the growth and development of an organism.

Ectoderm, Mesoderm, Endoderm

Germ layers

Ectoderm

• outermost germ layer

• Epidermis, nerves, hair, nails, nervous system

Mesoderm

• middle germ layer

• Skeletal system, muscles, gonads, connective tissues, circulatory system (heart and blood vessels), reproductive organs, kidneys, and the dermis of the skin.

Endoderm

• innermost germ layer

• Lining of digestive and respiratory tracts, & other organs such as liver, pancreas, and the lining of the urinary bladder.

Fertilization, Cleavage, Blastulation, Gastrulation

All vertebrate embryos undergo a similar pattern of development

Fertilization

• initial stage of development

• egg cell and sperm cell = zygote

Cleavage

Zygote undergoes rapid cell division = smaller cells are called blastomeres = morula

Blastulation

• Morula undergoes further cell division and rearrangement = blastula

• Embryo starts to form and have shape

Gastrulation

Blastula → embryo → structure with 3 germ layers

Homology

• is the similarity of structures because of similar embryonic origin and development. This is considered strong evidence of common descent.

• The bones that make up human fingers were inherited from an ancestor that is shared by all mammals. Bats, frogs, and horse also have these bones, but bats use them to spread their wings, and horse walk on them.

Homologous structures

are actual physical structures that show this similarity

Analogy

is the similarity of function and superficial resemblance of structures that have different origins/ ancestor.

Analogous structures

• are the actual body parts that look or act alike because they perform the same function, even though their embryonic origin is different.

• have different ancestry, but the same function.

• The wings of an insect, bird, and bat would all be ____: they all evolved to allow flight, but they did not evolve at the same time, since insects, birds, and mammals all evolved the ability to fly at different times.

Homoplasy

• is a shared character between two or more animals that did not arise from a common ancestor.

• It is the opposite of a homology, where a common ancestor provided the genes that gave rise to the trait in two or more animals.

• The body shape of sharks and dolphins is a _____. Both have a streamlined, fish-like shape for swimming fast, but sharks are fish, and dolphins are mammals. The similarity did not come from a common ancestor; it evolved independently

1809 in Shrewsbury, England

Charles Darwin was born in

Evolutionary biology

Charles Darwin (1809–1882) was an English naturalist, geologist, and biologist who is best known for his groundbreaking work in the field of _____.

On the Origin of Species

His most famous work, "______," published in 1859, introduced the theory of natural selection as the mechanism for the evolution of species

Galápagos Islands.

Darwin's observations and studies were influenced by his travels that took him to places like the _____

Natural selection

• is a simple mechanism that causes populations of living things to change over time. In fact, it is so simple that it can be broken down into five basic steps, abbreviated here as VISTA: Variation, Inheritance, Selection, Time, and Adaptation.

• Survival of the fittest

• Mechanism of evolution

• The nature’s method/mechanism

Variation

• Organisms can vary in size, coloration, ability to fight off diseases, and countless other traits.

• Small variations can influence whether an individual lives and reproduces. Differences in color, for instance, aid some individual organisms in camouflaging themselves from predators.

• Diversity of traits/characteristics

Inheritance

• Traits that contribute to an organism's fitness (its ability to survive and reproduce) are often passed on to the next generation.

• This means that the offspring of individuals with advantageous traits are more likely to inherit those traits.

• Advantageous traits - pass to offspring

• Traits are encoded in DNA; offspring often inherit the variations of their parents. Tall people, for example, tend to have tall children.

Selection

The process by which certain traits become more common or less common in a population based on their impact on survival and reproduction. This concept is fundamental in understanding how natural selection shapes the characteristics of species over time.

Time

• Natural selection is not an instantaneous process. It occurs gradually over many generations.

• The changes in a population's traits accumulate slowly as individuals with advantageous traits gradually outnumber those with less beneficial traits.

• The concept of time is crucial for understanding the long-term effects of natural selection on the evolution of species.

Adaptation

• After just a few generations or after thousands, depending on the circumstances, such traits become common in the population

• The result is a population that is better suited--better adapted--to some aspect of the environment than it was before

• The cumulative effect of VIST

• Result of natural selection process

Evolution

• In biology, ____ is the change in the characteristics of a species over several generations and relies on the process of natural selection.

• The theory of ____ is based on the idea that all species are related and gradually change over time.

• ____ → new species → diversity

• Origin, development, diversity of organisms

• No natural selection = no ____

Divergent evolution

• refers to the process by which interbreeding (can reproduce) species diverged into two or more evolutionary groups

• Homologous structure

• Over time, domestic dogs evolved into numerous breeds with distinct traits due to human selection and domestication, whereas gray wolves remained wild animals. Despite these behavioral and functional differences, their basic structure is still quite similar

Convergent evolution

• is the process whereby organisms not closely related have similar traits and features because of having to adapt to similar environments or ecological niches

• Analogus structure

• same environment = similar features

• Example: The body shape of sharks and dolphins is an example of ____, where two species from different evolutionary origin evolved similar features with slight differences to adapt to the same ecological niche—the aquatic environment. Their analogous structures (streamlined bodies and fins) are the result of adapting to similar environmental challenges

Parallel evolution

• the evolution of geographically separated groups in such a way that they show morphological resemblances

• It is the independent evolution of similar traits, starting from a similar ancestral condition.

• developed similar traits independently because of similar environment

• Homoplastic structure

• is provided by the two main branches of the mammals, the placentals and marsupials, which have followed independent evolutionary pathways following the break-up of landmasses such as Gondwanaland roughly 100 million years ago

Placentals and marsupials

One of the most common examples of parallel evolution is provided by the two main branches of the mammals, the _____ (humans, dogs, cats, horses, bats, elephants) and _____ (koalas, kangaroos, opossums)

Organic evolution

• is the process by which changes in the genetic composition of populations of organisms occur in response to environmental changes.

• Similar with functional adaptation

• Genetic mutation - changes in structure

• Anatomical changes

• Physical adaptation

• Behavioral traits

• Ecological relationship

Vestigial structure/organ or Remnants of ancestral traits

• is an anatomical feature or behavior that no longer seems to have a purpose in the current form of an organism of the given species.

• were organs that performed some important functions in the organism at one point in the past

• include the human appendix, human tailbone, the pelvic bone of a snake, and the wings of flightless birds.

Ontogeny

• is the development of a single individual, or a system within the individual, from the fertilized egg to maturation and death.

• study - development of an organism from fertilization to death

• alteration to genetic mutation

Process

1. Embryonic development

2. Growth

3. Differentiation of tissues and organs

4. Acquisition of specific structures, functions, and characteristics of mature organisms

Heterochrony

• is a change in relative timing of developmental processes.

• concept of evolutionary biology (changes in timing, stages, rate)

• alteration in process of developmental process = variation of organisms

• timing = stages of development

• It involves alterations in the timing of developmental processes, leading to variations in the timing of the appearance of certain traits or features in an organism's life cycle

• because of hormones and genetics (variation)