Bio 94 Midterm 3 Review Session Slides

Bio 94 Review

• Midterm 3

  • Tutors: Varun Ajith and Spencer Lam

Our Team

• Varun Ajith

  • Email: vajith@uci.edu

  • Availability: Thursdays 4-6pm, SH 239

• Spencer Lam

  • Email: spencel8@uci.edu

  • Availability: Mondays 3-5pm, SH 237

Disclaimer

• Review sessions duration: 2 hours

• Not all topics can be covered in depth.

• For deeper understanding, reach out via Discord.

Week 6 Review

Week 6 Lecture Overview

• Lecture 1: None (2nd Midterm!)

• Lecture 2: Intro to Animals

• Lecture 3: Protostomes

What is an Animal?

• Eukaryotic organisms

• Share a single common ancestor

• Monophyletic group

• Diversity began ~550 million years ago (Cambrian explosion)

• Approximately 30-35 phyla and 1.5 million species

What Makes an Animal an Animal?

1. Multicellular

   • Lack cell walls; possess extensive extracellular matrix (ECM)

2. Heterotrophic

   • Obtain carbon by consuming other organisms (not autotrophic)

3. Motile

   • Ability to move under metabolic energy at some stage of life

4. Neurons and Muscle Cells

   • Except sponges, neurons facilitate communication, muscle cells change body shape

Investigating Animal Evolution

1. Fossils

   • Provide records of transitional forms and adaptations

2. Comparative Morphology

   • Compare body structures among species, indicating evolutionary relationships

3. Comparative Development

   • Examines stages in embryonic development to establish relationships (eco-devo)

4. Comparative Genomics

   • Analyzes genetic information across species to find unique genes and evidence of natural selection

Comparative Development

• Diploblasts

  • Develop from 2 embryonic layers (e.g., jellyfish)

• Triploblasts

  • Develop from 3 embryonic layers (e.g., humans, worms)

Choanoflagellates

• Sessile protists, closest relatives to animals

• Use flagella for water movement, capturing bacteria

• Represent early transition to multicellularity

Phylum Porifera

• The most ancient group of animals

• Adults are sessile, with larval dispersal

• Often colorful, host symbiotic organisms

• Produce various toxins

Phylum Cnidaria

• Includes jellyfish, sea anemones, and corals

• Corals as ecosystem engineers (reefs)

• Sensitive to climate change impacts

• Three main aquatic lines:

  • Porifera

  • Ctenophora

  • Cnidaria

Key Transitions in Animal Evolution

1. Multicellularity

2. Complex Tissue Layers

3. Bilateral Symmetry

4. Origin of Gut and Coelom

Complex Tissue Layers

1. Ectoderm

   • Forms skin and nervous system

2. Mesoderm

   • Forms circulatory system, muscles, and bones

3. Endoderm

   • Forms lining of digestive and respiratory systems

Evolution of Bilateral Symmetry

• Linked to the development of a head and central nervous system

• Led to the radiation of bilateral animals (radial symmetry evolved independently)

Gut and Coelom

• Tube-within-a-tube body plan

  • Gut allows for material flow from mouth to anus

  • Coelom: body cavity lined with mesoderm

  • Protostomes develop mouth first; deuterostomes develop anus first

Coelom Types

1. Coelomates

   • Fully lined coelom

2. Acoelomates

   • No body cavity

3. Pseudocoelomates

   • Partially lined body cavity

Diversification Themes in Animal Phyla

• Sensory organs: developed for sight, hearing, etc.

• Feeding Methods:

  • Diet Types: detritivores, herbivores, carnivores, omnivores

  • Feeding Modes: suspension, deposit, fluid, mass feeders

Animal Reproduction and Life Cycles

• Modes: Asexual and Sexual

• Embryo Development: Viviparous (live birth), Oviparous (egg), Ovoviviparous (eggs hatch internally)

• Life Cycles can involve Metamorphosis

Overview of Protostomes

• One of the five major lineages of animals

• Bilateral and triploblastic

• Not deuterostomes

Ecosystem Services of Protostomes

• Benefits like pollination, pest control, nutrient regeneration

Themes of Protostome Diversification

• Adaptations for aquatic to terrestrial transitions

• Innovations for gas exchange, desiccation, and structural support

Compartmentalization in Body Plans

• Enables evolutionary changes in specific areas without affecting others

Major Protostome Phyla

1. Platyhelminthes: Flatworms, include parasites

2. Annelida: Segmented worms, improve soil fertility

3. Mollusks: Clams, slugs, squids, octopi, open circulatory system

Ecdysozoa Synapomorphy

• Molting (releasing exoskeletons)

Nematodes

• Roundworms, typically small and unsegmented

• Numerous species with diffusion-based nutrient transport

Tardigrades

• Water bears; survive extreme conditions

Characteristics of Arthropods

1. Exoskeleton of chitin

2. Segmented body into tagmata

3. Jointed appendages

Insect Diversity

• Evolution of wings for powered flight

• Metamorphosis as a transformation method

Week 7 Review

Week 4 Lecture Overview

• Lecture 1: None (President’s Day!)

• Lecture 2: Deuterostomes Part 1

• Lecture 3: Deuterostomes Part 2

Deuterostome Overview

• Include largest and most complex animals

• Previously grouped based on mouth development (now found to be incorrect)

Echinodermata Characteristics

• Marine organisms include sea stars, sea urchins

• Radial symmetry, endoskeleton of calcium carbonate

• Water vascular system

Chordata Characteristics

• Four defining traits:

  1. Pharyngeal slits/pouches

  2. Dorsal hollow nerve cord

  3. Notochord

  4. Muscular, post-anal tail

Vertebrate Innovations

• Synapomorphies such as vertebrae and cranium

• Early vertebrate fossils using CT scan reveal ancestral traits

Innovations in Vertebrates

• Evolution of jaws, bones, and limbs for terrestrial transition

Amphibians

• Key adaptations: limbs (water-to-land), amniotic eggs

Mammals

• Three lineages of mammals: monotremes, marsupials, placentals

Reptiles

• Include scales and adaptations; birds are considered reptiles due to shared characteristics

Primates

• Divided into prosimians and anthropoids; characterized by grasping hands, forward-facing eyes

Hominins

• Humans as bipedal great apes; relatives include bonobos and chimpanzees

Out-of-Africa Hypothesis

• Suggests Homo sapiens evolved in Africa before migrating globally with some interbreeding evidence

Human Evolution Today

• Discuss lactose intolerance and effects of co-evolution with bacteria

Week 7 Questions

• Fill out evaluation form

Final Exam Review

Key Concepts Covered

Eucaryotic origins, diversity, evolution patterns, behavioral ecology

Ecological Study Levels

• From globe to organism, including population and community dynamics

Abundance and Distribution Factors

• Abiotic Factors: sunlight, soil, nutrients

• Biotic Factors: species interactions

Climate vs Weather

• Weather as short-term conditions, climate as long-term predictions related to geography

Global Patterns

• Influences of solar angles, ocean currents on ecosystems

Terrestrial Biomes

• Characterized by unique abiotic factors and vegetation types

Aquatic Biomes

• Recognized for nutrient, sunlight, and salinity characteristics

Human Impacts on Ecosystems

• Refers to pollution, invasive species and various ecological changes

Behavioral Ecology

• Discussion of proximate and ultimate causation of behaviors; innate vs learned behaviors

Communication Types

• Signal processing in behavior modification for survival and mating

Fitness Trade-offs

• Understanding the complexity of animal behavior and selection

Cooperation and Kin Selection

• Altruism profile based on inclusive fitness and Hamilton's Rule

Evolutionary Game Theory

• Predictive models analyzing evolutionary interactions among organisms

Final Evaluation

• Reflect on course, submit feedback forms

Thank You!

• Please fill out the Evaluation Form; resources will be shared post-evaluation.