|Sharon Holte, Florida Museum of Natural History Maggie Paxson, Gainesville High School in collaboration with Victor Perez, Florida Museum of Natural History and Alex Lounders, University of Florida||9th-10th Grade Biology, Potentially Advanced Middle School Life Science||10 minutes of one class period before a weekend, then three full 50 minute class periods for lesson implementation|
How does forelimb anatomy impact the predation strategies of cat and dog relatives?
This lesson will guide students through the various ecological and anatomical characteristics of modern, charismatic cats and dogs. They will then use extrapolation to make interpretations about the characteristics that lead to success in different ecosystems. Students will use 3D-printed forelimb bones of modern dogs and cats as well as fossil dogs to examine physical evidence of bone rotation, and will then link these functions to relative likelihood of survival in ecosystems with different prey animals. Students will end with a discussion of fossil dogs and two “strange” modern animals that do not fit into the cat or dog osteological models, and the students will draw conclusions about what this anatomy suggests about these animals’ niches and evolutionary relationships relative to other examined species.
Next Generation Science Standards (NGSS)
LS4.A: Evidence of Common Ancestry and DiversityGenetic information provides evidence of evolution. DNA sequences vary among species, but there are many overlaps; in fact, the ongoing branching that produces multiple lines of descent can be inferred by comparing the DNA sequences of different organisms. Such information is also derivable from the similarities and differences in amino acid sequences and from anatomical and embryological evidence. (HS-LS4-1)LS4.B: Natural SelectionNatural selection occurs only if there is both (1) variation in the genetic information between organisms in a population and (2) variation in the expression of that genetic information—that is, trait variation—that leads to differences in performance among individuals.(HS-LS4-2)LS4.C:Evolution is a consequence of the interaction of four factors: (1) the potential for a species to increase in number, (2) the genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for an environment’s limited supply of the resources that individuals need in order to survive and reproduce, and (4) the ensuing proliferation of those organisms that are better able to survive and reproduce in that environment.(HS-LS4-2)
Connection to Lesson
|HS-LS4-1: Communicate scientific information that common ancestry and biological evolution are supported by multiple lines of empirical evidence.||Students will compare forelimb anatomy for multiple species of cats and dogs, and link anatomical features to change over time. Students will be able to integrate this information with previously discussed evolutionary concepts.Students will compare forelimb anatomy for multiple species of cats and dogs, and link anatomical features to change over time. Students will be able to integrate this information with previously discussed evolutionary concepts.|
|HS-LS4-2: Construct an explanation based on evidence that the process of evolution primarily results from four factors: (1) the potential for a species to increase in number,
(2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those
organisms that are better able to survive and reproduce in the environment.
|This lesson’s conclusion allows students to use forelimb anatomy as an example of different phenotypes that enable differential survival. Students will examine the niches of various carnivores and link their bone anatomy to these roles in the environment. Students will then discuss how different structures enabled differentiated competition, and as a result, survival and reproduction.|
Science & Engineering Practices
Connection to Lesson
|Obtaining, Evaluating, and Communicating Information
Obtaining, evaluating, and communicating information in 9–12 builds on K–8 experiences and progresses to evaluating the validity and reliability of the claims, methods, and designs.
Constructing Explanations and Designing Solutions
Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are
|Obtaining, evaluating, and communicating information: Students will work in cooperative groups to observe forelimb anatomy and describe differences to lab partners. Students will then work cooperatively (on day 3) to design an ideal environment for an unknown predator.
Constructing explanations and designing solutions: Students will seek to explain niche and relative hunting strategy in relation to an organism’s bone anatomy. Students will then compare their hypotheses with established scientific ideas on the evolution of carnivores and bone anatomy.
Disciplinary Core Ideas
Connection to Lesson
|LS4.A: Evidence of Common Ancestry and Diversity
Genetic information provides evidence of evolution. DNA sequences vary among species, but there are many overlaps; in fact, the ongoing branching that produces multiple lines of
descent can be inferred by comparing the DNA sequences of different organisms. Such information is also derivable from the similarities and differences in amino acid sequences and
from anatomical and embryological evidence. (HS-LS4-1)LS4.B: Natural Selection
Natural selection occurs only if there is both (1) variation in the genetic information between organisms in a population and (2) variation in the expression of that genetic information—that is, trait variation—that leads to differences in performance among individuals. (HS-LS4-2)LS4.C: Adaptation
Evolution is a consequence of the interaction of four factors: (1) the potential for a species to increase in number, (2) the genetic variation of individuals in a species due to
mutation and sexual reproduction, (3) competition for an environment’s limited supply of the resources that individuals need in order to survive and reproduce, and (4) the ensuing
proliferation of those organisms that are better able to survive and reproduce in that environment. (HS-LS4-2)
|LS4.A: Students are comparing morphological structures and how they relate to function. This activity could easily be extended to also examine differences in DNA structures or amino acid sequences.
LS4.B: Students will engage in discussion regarding how anatomical diversity leads to differentiated survival and reproduction, thus supporting the theory of natural selection. Students will compare trait variations and analyse how these enable organisms to survive in diverse ecosystems.
LS4.C: Students will link differentiated survival as a result of varying bone anatomy to competition, and an organism’s ability to compete for resources and reproduce.
Connection to Lesson
Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in
explanations of phenomena.(HS-LS4-1)Cause and Effect
Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects.
|Patterns: Students are examining comparative anatomy and looking for similarities in bone anatomy that then leads to different hunting strategies.
Cause and effect: Students will examine one of the fundamental concepts of evolutionary biology, that “function follows form.” Students will analyse comparative anatomy and link these differences in bone structure to their function—for example differences in running predators that hunt by exhausting prey and those predators who supinate their wrists and are ambush predators.
- 912.L.15.1: The scientific theory of evolution is the fundamental concept underlying all of biology.
- The scientific theory of evolution is supported by multiple forms of scientific evidence.
- Organisms are classified based on their evolutionary history.
- Natural selection is a primary mechanism leading to evolutionary change.
- 912.L.15.4: Describe how and why organisms are hierarchically classified and based on evolutionary relationships.
- 912.L.17.6: Compare and contrast the relationships among organisms, including predation, parasitism, competition, commensalism, and mutualism.
Show Discovery News clip titled “When did dog’s become man’s best friend?”:
This 3:12 long video describes the early branching of dogs from ancestral carnivorans, and how modern scientists have used fossil and molecular biological evidence to trace the origins of the domesticated dog to more than 25,000 years ago. Additionally, the clip introduces students to the use of 3D morphology, a practice they will be using in this lesson to compare dog and cat anatomy.
Possible Discussion Questions:
- How does dog breed diversity affect their popularity and evolutionary relationship with humans?
- Why is it so difficult to figure out how long ago dogs were domesticated?
- Why would scavenging alongside humans be an evolutionary adaptation for dogs?
- How is the early human-dog relationship an example of mutualism?
- How did the incredible diversity in dog breeds come about so quickly?
In this lesson, students will collaborate using a jigsaw model to first master information on two modern animals, one cat and one dog, and will then teach their peers about these animals. By cooperative grouping, students will use researched information to explain the anatomical and ecological features that have enabled various species to survive in different biomes, and will then extend this information to create over-arching ideas about the importance of anatomical differences in evolutionary advantages for survival and reproduction. Over the course of this lesson, students will create two posters in groups, and will rely on oral presentation skills to teach their peers about the two organisms they have learned about.
Like real paleontologists, students will look at comparative anatomy and draw conclusions about evolutionary relationships and predatory-prey relationships. This lesson includes the use of 3D morphometrics, a fairly recent innovation in the field of paleontology that looks to the comparative analysis of modern and fossil bones to answer questions about evolutionary relationships, ecological roles, and other aspects of modern and paleo-biology. Students will use skills learned during the first two days of the lesson to engage in a basic, morphometric analysis of an unknown bone, and to draw conclusions about that “mystery organism’s” ecological niche and habitat.
Student record sheets from homework assignments are checked for completion or accuracy (teacher’s discretion). It is recommended teachers check or stamp the completed worksheets as they circulate the room observing students working on their posters during Day 1. Day 1 posters may be graded by teachers if they choose, or a participation grade may be given based on the teacher’s own classroom policies. Alternatively, teachers may rely on summative assessment on day one (circulating the room, checking for active participation in all groups, asking questions of the students who seem disengaged, etc.) and use the record sheets generated on Day 2 as formal assessments.
Students will complete record sheets during their gallery walk. These record sheets should be completed by the end of Day 3 and turned in at the lesson’s culmination. Teachers may grade these based on their own classroom and grading policies.
The group poster project should be assessed using the following rubric: Download Poster Rubric
|The poster includes all required elements as well as additional information. Students have described the organism’s niche, ecosystem, predation, and other information relevant.||All required elements are included on the poster. Organism’s niche, ecosystem, and predation style are well described.||All but 1 of the required elements are included on the poster.||Several required elements were missing. Organism’s niche or ecosystem are weakly explained.|
|The student has used the anatomy of the 3D printed bone to justify all aspects of the scientific information contained on the poster.||Most information contained on the poster is justified using the anatomy of the bone.||Only predation style, niche, or ecosystem are well justified using the anatomy of the bone, and the poster may rely heavily on prior knowledge or outside information (other than the bone).||Poster is primarily comprised of speculative information that is not justified using the bone\’s anatomy.|
Use of Terminology
|At least 7 accurately used terms are displayed on the poster.||5-6 accurately used terms are displayed on the poster.||3-4 accurately used terms are displayed on the poster.||Less than 3 accurately used terms are displayed on the poster.|
Graphics – Relevance
|All graphics are related to the topic and make it easier to understand. All borrowed graphics have a source citation.||All graphics are related to the topic and most make it easier to understand. All borrowed graphics have a source citation.||All graphics relate to the topic. Most borrowed graphics have a source citation.||Graphics do not relate to the topic OR several borrowed graphics do not have a source citation.|
|The poster is exceptionally attractive in terms of design, layout, and neatness.||The poster is attractive in terms of design, layout and neatness.||The poster is acceptably attractive though it may be a bit messy.||The poster is distractingly messy or very poorly designed. It is not attractive.|
Post Lesson: Student paragraphs should be collected after completion of the lesson. These can be turned in separately or with other materials at the teacher’s preference.
Assessment Summary: Download PDF
Suggested point Value
Type of Assessment
|Pre-Lesson Homework||Students complete record sheet at home regarding their assigned organisms (Prior to lesson’s beginning)||15||Worksheet-Summative if checked for completion, Formative if used to reinforce misconceptions or inaccuracies||Scaffold assignment, practice research skills|
|Gallery Walk Record Sheets||Students record information on all species based on information taught by peers (Day 2)||20||Worksheet-Formative||Practice teaching to each other, oral presentation, core ideas|
|Hypothetical Ecosystem Poster||Students create posters in their home groups that describe the hypothetical ecosystems and niches of unknown organisms.||20||Poster-Formative (rubric above)||Evaluate information learned and gathered thus far, synthesise into cohesive form.|
|Final Reflection Writing Assignment||Students summarise what they have learned in a paragraph that analyses their previous assignment.||20||Summative, Writing||Writing practice skills|
Total Point Value: 75
This lesson follows a rough jigsaw format (see resources) to organize students into Master Groups (based on Kagan group strategies) to create posters on Day 1 about their assigned animals, then to teach their peers about their assigned animals using a gallery walk on Day 2. On Day 3, all students come together in Home Groups to discuss three “unknown” animals and describe their likely evolutionary and ecological orientations.
DAY 0 (Prequel):
Day 0 should be a 10 minute period at the end of a class about evolution and relationships between different predators and prey. Pass out the homework worksheet and assign each student one cat and one dog to research over the weekend (worksheet below). Students should research the niche and relationships of their two assigned organisms in preparations for Day 1’s class. Students will be responsible for researching their assigned species over the weekend Organisms can be randomly assigned or assigned so that eventual Master groups use Kagan Grouping models at the teacher’s discretion. Regardless, each dog and each cat should be paired using the table below, and assigned so that 5-6 students receive each pairing.
|2||Mountain Lion||Bush Dog|
|6||Domestic Cat||Domestic Dog|
Master Groups for Anatomical and Niche Comparison
Students assigned the same pairs of animals will make up each “master group.” Over the course of Day 1, students are responsible for organizing their information into a divided poster— ½ for their assigned cat and ½ for their assigned dog. Posters should include all necessary information regarding organism’s niche, evolutionary history if appropriate, and interesting facts the students researched. Students will then receive 3D printed models of their assigned organism’s forelimb bones, and will draw the bones and make osteological inferences based on provided.
30 Minutes: Poster
- Materials: Art supplies, meter sticks, poster/butcher paper, potential internet access, and student worksheets from Day 0.
- Instruct students to get in groups based on who were assigned the same pair of organisms. Students have 30 minutes to create a divided poster that displays all the relevant information about their cat species on one half and their dog species on the other half. If students finish early, they may receive the 3D-printed bones of their assigned species and begin taking observations.
- Specific poster requirements may be altered or graded based on teacher preference, or students can be judged for participation and effort because the information from them will be graded the following day.
- Required elements each poster should include for each organism:
• Species name
• Niche (prey animals, any predators, sociality if applicable, etc.)
• Conservation status
• Special adaptations the organism has evolved for surviving in its specific habitat
15 Minutes: Observations
Students should take careful observations of the two bones they are examining. Instruct students to look for both differences and similarities, though broad categories like size and general shape should be avoided.
- Materials: 3D-printed bones, one per group each of cat and dog, bone worksheets, and bone reference sheets (see attached resources below).
- Encourage students that artistic talent is not necessary to be a good scientist! Observations and drawings should be as detailed as possible, but students should not stress about whether they are “good at art.” Encourage all students to annotate and label their drawings as these observations will be helpful later. Teachers can have students record their observations on a blank sheet of paper to turn in at the end of class or to keep for reference.
- Students should make note of any unique foramen, fossa, tubercles, tuberosities, and ridges, and they should do their best to draw their bone and its features with appropriate proportions.
Advanced Preparation for Day 2: After class, the teacher should hang posters at evenly spaced increments around the classroom with the respective 3D-printed bones in front.
Gallery Walk and Orienting Other Cat and Dog Species
Students spend Day 2 doing a gallery walk. Each Master Group should be randomly numbered 1-5(6) to create new Home Groups. Students should re-divide into their Home Groups and spend ~8-10 minutes at each poster in a gallery walk (see resources). At each poster, the respective “expert” should explain the animals for group members to take brief notes on their record sheets. Students should also note differences in bone anatomy between cat and dog species (See record sheets attached), and any notable differences between the bones of the organisms they are examining and their own assigned species.
Identifying Unknown Species and Comparing Fossil Bones
Students spend Day 3 comparing unknown, atypical organisms (a cheetah and a hyena) and then a fossil dog. Students use prior knowledge of bone anatomy and the corresponding ecological roles to determine if unknowns are cats, dogs, or other.
Students spend Day 3 comparing two unknown, atypical organisms (a cheetah and a hyena) and then a fossil dog. Students use prior knowledge of bone anatomy and the corresponding ecological roles to determine if their unknowns are cats, dogs, or another type of animal.
10 Minutes: Comparative anatomy of unknown forelimbs and fossil dog forelimb
Students work in Home Groups to identify the approximate classification of the three provided organisms. Each Home Group will be assigned one of the three unknowns and will replicate observations from the previous days. Two groups should be each assigned the modern cheetah, two the spotted hyena, and two the Metatomarctus extinct dog. Instruct each group to record observations and a drawing of their assigned unknown bone on their record sheet (see below). Students should discuss the anatomy of the 3D-printed bone within their Home Groups to determine if it is more cat-like or dog-like, and what this means about their unknown organism’s possible niche.
Based on teacher preference, all students may record notes, or one student may act as a record keeper to record notes for the next portion of the assignment.
30 Minutes: Designing a habitat for an assigned unknown.
Students will create a habitat, prey, and generalized niche for their unknown organism based on comparisons with the previous day’s observations. Ideally, students will have figured out if their animal was more cat-like or dog-like, and will use this to guide their hypothetical habitat. See rubric (made using Rubistar online) for grading instructions.
Tell students their posters should contain scientifically accurate language and information, and any decisions they make about their hypothetical ecosystem and the niche of their mystery species should be justified by the bones. Encourage students to compare the mystery bone they are examining to their drawings and observations from the previous two days.
Remind students that in evolutionary biology, function follows form! The morphology of an organism usually dictates its adaptations, predation style, locomotion—everything! Similarities between their unknown organism and some of the specimens from the previous days could mean the two species share similar traits or roles in their respective environment. For example, a long-limbed organism is likely better at running great distances than a short-limbed animal.
10 minutes: Wrap-up Discussion/Reveal
The last 10 minutes of the class should be reserved to reveal which species the student groups have received and to give a description of the actual habitat.
- See downloadable PowerPoint Presentation descriptions of the three unknown organisms to share with students if time permits.
- Potential discussion questions:
- What about your organism’s bone anatomy makes sense now that you know what it is?
- Was it difficult to determine whether your unknown was more like a cat or a dog? Why or why not?
- What aspects of the unknown bones did you feel give you the biggest clues to its ecological niche and predation style?
- Did anything about the mystery bones confuse you? Why was this the case?
- Does anything about your species’ bone surprise you now that you know what it is? (Note: Many students will recognize that the hyena, which is actually a closer relative of Felidae than Canidae, provides an interesting “in-between” specimen for the two clades. Students may find this odd or surprising because hyenas appear generally dog-like in their morphology.
- How does your mystery organism’s forelimbs make it suited for its role in its respective habitat?
- How would you expect the population of each mystery organism to change if the environment changed suddenly and drastically? How might this be reflected in the anatomy? (Note: Teachers may use this as a potential discussion on global climate change. Because the two extant mystery animals live in Sub-Saharan Africa, they are at a greater risk of extinction from climate change than more temperate species.)
- Students should write a well-developed paragraph on the mystery organism they were assigned that answers the following questions:
- Based solely on the bone anatomy, what did you think your animal was or what did it look like (i.e., anatomical features, predation style, cat or dog like, etc.)?
- Which of your predictions (for your habitat or your organism) were accurate and what about your bones led you to these accurate conclusions?
- Which of your predictions were inaccurate and why did you believe these inaccuracies based on the bone you examined?
Resources & Materials
- 3D STL Files for this lesson are available for free download at: http://morphosource.org/MyProjects/Dashboard/dashboard/select_project_id/356
- Manipulate 3D models in MeshLab:http://www.meshlab.net/ (Note: Meshlab can be used to measure and manipulate STLs. As the provided scans in Morphosource are high quality, this could potentially be used as an extension for extremely interested learners or future projects.)
- We also recommend Google Chrome 3DView, which is free, web-based 3D Model viewer with measuring capabilities.
- Anatomy of the upper limbs: https://www.getbodysmart.com/ap/skeletalsystem/skeleton/appendicular/upperlimbs/menu/menu.html
- Washington State University College of Veterinary Medicine Musculoskeletal interactive: https://www.vetmed.wsu.edu/outreach/Pet-Health-Topics/categories/cat-and-dog-anatomy/the-musculoskeletal-system
Evolution Teaching Resources
- PBS Evolution Resources: http://www.pbs.org/wgbh/evolution/
- University of California Berkley Evolution teaching resources: http://evolution.berkeley.edu/evolibrary/teach/
- Excellent game-style simulator for natural selection from the University of Colorado, Boulder, PHET: https://phet.colorado.edu/en/simulation/natural-selection
Ecology Teaching Resources
- Ecological Society of America Teaching Resources page: https://www.esa.org/esa/education-and-diversity/educator-resources/
- Pearson predator-prey simulation: http://www.phschool.com/atschool/phbio/active_art/predator_prey_simulation/
- Khan Academy article on niches and competition: https://www.khanacademy.org/science/biology/ecology/community-ecosystem-ecology/a/niches-competition
- Online glossary of paleontology: com/paleontology/glossary.html
- Another online paleontology glossary: fossilmall.com/Science/Glossary.htm
- Origins of the group Carnivora: http://mypage.iu.edu/~pdpolly/Papers/Polly%20et%20al,%202006,%20Viverravus.pdf
- Major patterns in the history of carnivorous mammals: http://www.annualreviews.org/doi/abs/10.1146/annurev.earth.27.1.463?journalCode=earth&
Classification and Biodiversity Resources
- Mammalian Diversity: http://animaldiversity.org/accounts/Mammalia/
- Online animal encyclopedia with varying degrees of information for different species: https://a-z-animals.com/animals/
- Linnaean classification from the City University of New York: http://www.brooklyn.cuny.edu/bc/ahp/CLAS/CLAS.Linn.html
Useful Videos (Potentially useful for prior lessons, wrap-up, or in the event of extra time on any day)
- “The Science of a Cheetah’s Speed,” National Geographic: https://www.youtube.com/watch?v=icFMTB0Pi0g
- Hank Green’s “Comparative Anatomy” Crash Course: https://www.youtube.com/watch?v=7ABSjKS0hic
- Hank Green’s “Taxonomy” Crash Course: https://www.youtube.com/watch?v=F38BmgPcZ_I
- Digital recreation of lion locomotion: https://www.youtube.com/watch?v=VrZd4UNF41E
- Homologous structures in organisms: http://study.com/academy/lesson/homologous-structures-comparison-of-body-structures-across-species.html
- Using the Jigsaw method in the classroom: http://www.readwritethink.org/professional-development/strategy-guides/using-jigsaw-cooperative-learning-30599.html
- Using the “Gallery Walk” strategy in the classroom: http://www.theteachertoolkit.com/index.php/tool/gallery-walk
- Rubric for Day 3 poster created using Rubistar, a free online tool for teachers (registration required): http://rubistar.4teachers.org/index.php
Individual Species Resources (Most from IUCN Red List)
- Grey Wolf: http://www.iucnredlist.org/details/3746/0
- Bush Dog: http://www.iucnredlist.org/details/20468/0
- Red Fox: http://www.iucnredlist.org/details/23062/0
- Arctic Fox: http://www.iucnredlist.org/details/899/0
- Coyote: http://www.iucnredlist.org/details/3745/0
- Domestic Dog: http://bioweb.uwlax.edu/bio203/s2009/nyberg_mich/index.htm
- Lion: http://www.iucnredlist.org/details/15951/0
- Mountain Lion: http://www.iucnredlist.org/details/18868/0
- Ocelot: http://www.iucnredlist.org/details/11509/0
- Clouded Leopard: http://www.iucnredlist.org/details/14519/0
- Bobcat: http://www.iucnredlist.org/details/12521/0
- Domestic Cat: http://www.sms.si.edu/irlspec/felis_catus.htm
- Photographs of animals: http://www.arkive.org/
- See attached PowerPoint Slides or download the editable PowerPoint on all of these organisms from the iDigFossils page for this lesson. http://idigfossils.org
Due to the jigsaw nature of this activity, there are multiple methods of differentiation for class size, learning ability, time availability, etc.
Class Size: Larger class sizes could be dealt with using partners. Instead of individuals being assigned, teams could be assigned for some organisms to increase the number of students participating. Smaller classes can exclude a pair or two of the organisms, though it is not recommended to exclude the domestic species due to relatability.
Ability: More advanced classes can be encouraged to do more in depth research or extension projects on their assigned master species or the unknowns given at the end of the lesson. Less experienced learners or researchers can be provided with the individual species resources given in the resources section of this lesson or can be given additional time for the various aspects of this lesson plan.
Timing: This lesson is more easily extended than shortened. The gallery walk (Day 2) could easily be extended for an additional half day to increase time for discussion. Likewise, creating the hypothetical environment and wrap up discussions could be extended. To shorten this lesson, larger groups can be used with fewer pairs of organisms (thus shortening the times for the poster design and gallery walk on Day 1 and Day 2, respectively).
Key Academic and/or Scientific Language
Abiotic: the nonliving components of an environment
Allele: a variation or version of a gene
Anterior: oriented facing forward or a forward view (opposite of posterior – see Directional References)
Barbourofelidae: an extinct family of felid-like carnivorans (see Carnivoran Phylogeny)
Biome: a large, naturally occurring community of flora and fauna occupying a major habitat with common patterns in climate and similar soils, e.g., forest or tundra
Biotic: the living components of an environment
Canidae: a family in the Order Carnivora that includes animals such as domestic dogs, wolves, foxes, jackals, dingoes, and others (see Carnivoran Phylogeny)
Capitulum of the humerus: the lateral portion of the distal articular surface consisting of a smooth,
rounded eminence (see Comparative Bone Chart)
Carnivora: a diverse order that includes over 280 species of placental mammals
Carnivoran: a member of the Order Carnivora
Carpals: bones in the proximal section of a hand, the wrist
Cat Gap: a period in the North American fossil record dating to approximately 25 to 18.5 million years ago in which there are no fossils of cats (members of Felidae) or cat-like species (members of the Families Nimravidae and Barbourofelidae) (see Geologic Timescale)
Competition: the ways in which organisms compete directly for scarce or limited resources such as food, water, space, and mates
Differential survival and reproduction: the basis of natural selection. Differences in phenotype cause different individuals to survive and reproduce at different rates
Distal: organ, bone, or feature situated away from the center of the body or from the point of attachment (opposite of proximal – see Directional References)
Ecology: the study of interactions between the biotic and abiotic components of an environment, and how living things compete for resources
Ecosystem: a biological community of interacting organisms and their physical environment
Evolution: the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth
Extant: organisms that are still alive or modern
Extinct: organisms that are no longer alive and have all died out
Felidae: a family in the Order Carnivora that includes animals such as domestic cats, mountain lions, cheetahs, tigers, and others (see Carnivoran Phylogeny)
Foramen: a hole or passage in a bone (see Comparative Bone Chart)
Fossa: a depression or hollow in a bone (see Comparative Bone Chart)
Fossil: the preserved remains or traces of animals, plants, and other organisms from the remote past
Gene: a section of DNA that codes for a protein, thus conferring a trait on an organism
Heritable: transmissible genetic characteristic from parent to offspring
Homologous structures: an organ, bone, or feature that appears in different animals but is similar in structure or function, underlining anatomical commonalities demonstrating descent from a common ancestor
Humerus: long bone in the upper arm or forelimb that runs from the shoulder to the elbow
Hyaenidae: the fifth-smallest biological family in the Order Carnivora with only four extant species. More closely related to cats than dogs (see Carnivoran Phylogeny)
Interspecific competition: competition between organisms of different species
Intraspecific competition: competition between organisms within a species
Lateral: used to refer to structures away from the center or mid-line of a body (opposite of medial – see Directional References)
Linnaean Classification: also known as dichotomous classification, species are defined using a two name system of genus and species
Macroevolution: applies mainly to the evolution of whole taxonomic groups over long periods of time
Medial: used to refer to structures close to the center or mid-line of a body (opposite of lateral – see Directional References)
Metacarpals: the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist
Miocene: the fourth epoch of the Tertiary period, between the Oligocene and Pliocene epochs, approximately 23.03 to 5.3 million years ago (see Geologic Timescale)
Morphology: the branch of biology that deals with the form of living organisms and with relationships between their structures
Natural Selection: the differential survival and reproduction of individuals due to differences in
Niche: the role and position a species has in its environment, all of its interactions with the biotic and
abiotic factors of its environment
Nimravidae: an extinct family of felid-like carnivorans (see Carnivoran Phylogeny)
Osteology: the study of the structure and function of the skeleton
Phalanges: small bones that make up the fingers of the hand and the toes of the foot
Phenotype: the physical manifestation of an organism’s genetics, e.g., what an organism looks like
Phylogenetic: the evolutionary development and diversification of a species or group of organisms
Posterior: oriented facing backwards, or a view from behind (opposite of anterior – see Directional References)
Predation: in an ecosystem, predation is a biological interaction where a predator (an organism that is hunting) feeds on its prey (the organism that is attacked)
Predator-Prey relationship: a predator is an organism that eats other organisms, prey, for sustenance. The relationship refers to the interconnectedness of two or more populations in which one predates another, thus influencing its numbers
Pronation: the natural inward roll of a foot or hand during locomotion
Proximal: organ, bone, or feature situated nearer to the center of the body or the point of attachment (opposite of distal – see Directional References)
Radius: one of two bones in the forearm that runs from the elbow to the first digit (thumb in humans) and enables radial movement
Selective advantage: characteristic of an organism that enables it to survive and reproduce better than other organisms in a population in a given environment
Selection pressures: an agent of differential mortality or fertility that tends to make a population change genetically
Supination: the natural outward roll of a foot or hand during locomotion
Taxonomy: the branch of science concerned with classification, especially of organisms
Trochlea of the humerus: the medial portion of the articular surface of the elbow joint which articulates with the proximal end of the ulna in the forearm (see Comparative Bone Chart)
Tubercle: a small rounded projection or protuberance on a bone (see Comparative Bone Chart)
Tuberosity: a large prominence on a bone usually serving for the attachment of muscles or ligaments (see Comparative Bone Chart)
Ulna: one of two bones in the forearm that runs from the elbow to the lateral most digit (the pinky in humans)
Ultimately, this lesson plan seeks to enhance students’ understanding of the theory of evolution by means of natural selection. Evolution is the gradual change in populations over time due to environmental pressures placed on these organisms. Evolution is both a random and non-random process. During sexual reproduction, organisms inherit a random assortment of alleles from each of their biological parents. The unique combinations of alleles inherited by an offspring leads to their specific phenotype, which ultimately determine an organism’s likelihood to survive and thus reproduce. While the assortment of inherited alleles is random due to meiosis and fertilization, the differential survival resulting from these alleles is not. Natural selection refers to the natural selection pressures that act on allele combinations, leading to changes in allele frequencies because certain alleles are favorable for survival or reproduction.
Ecology refers to the study of interactions between the biotic and abiotic environments. One of the primary ways organisms interact is through competition, or the many ways in which organisms compete for resources, space, mates, and other necessities. Interspecific competition is when different species compete for common resources. The organisms born with better adapted alleles are more likely to win outright in these instances of competition, thus leading to macroevolution. Sometimes, competition selects for different traits in separate groups of organisms. The cat and dog families, for example, exhibit very different forelimb anatomy as a result of different predation strategies: dogs tend to be running, pack hunters, while cats are often ambush attack predators. These different strategies are seen in the straight, fused forelimbs of dogs and the rotating forelimbs of cats.
Overall, organisms that have evolved over time into different groups are organized using Linnaean Classification. Also called dichotomous classification, this system assigns scientific names to all described organisms using a binomial form. This lesson may be used to introduce or expand upon a discussion of classification using the reference table below. As scientists learn more about different species of animals, their taxonomy may change. Species are constantly being renamed, regrouped, and reclassified so it is important to understand that species names may change through time. For example, the arctic fox (Vulpes lagopus) used to be classified in the genus Alopex but today, scientists believe that it is more closely related to the red fox (Vulpes vulpes) and have reclassified its genus to Vulpes.
Ultimately, the goal of this lesson plan is to lead students to draw connections between extant species of carnivorans and extinct dogs. Evolutionarily, all mammals share a common ancestor, a “furry, tailed, quadruped” as Darwin called it. Modern organisms with common ancestors retain similar morphological traits, which are often displayed as homologous structures. The forearms of most mammals, for example, contain the same general osteology: radius and ulna in the lower part of the limb, humerus in the upper part. While similar in general shape, length relative to the body, and structure, these bones contain species-level differences that ultimately lead to differences in function and use by the organism. By comparing the similar morphologies of modern and extinct species, students can deepen their understanding of evolutionary relationships and the variable traits that arise from natural selection.
More specifically, this lesson examines the distinct roles of cats and dogs and the ecological niches that come as a result of their different anatomy. Overall, dogs tend to hunt in packs, and they often run down prey. This is seen in upper limb bones that are more adapted for running over long distances. Dogs also lack the ability to rotate their forelimbs, something every cat owner witnesses every time their pet plays with, bats at, or captures toys or living prey animals. The ability of cats to supinate their wrists enables more solitary or ambush hunting, though some species (Panthera leo, the African lion, for example) certainly hunt in prides or packs.
One interesting extension of this lesson is to discuss the “Cat Gap,” a time period in North American history ranging from approximately 16-21 million years ago when fossil Felids and cat-like Nimravids and Barbourofelids were nonexistent in the fossil record. During this period, several species of fossil dogs (including Metatomarctus canavus) demonstrate forelimb anatomy that is similar to cat forelimbs in several prominent features (see final bone chart appendix of this lesson plan). Day 3 of this lesson plan seeks to explore these intermediate phenotypes and correlate them to an approximate niche.