11.2: Introduction - Biology

The two questions you answered above are essential to understanding the evolution of secondary growth. In secondary growth, primary tissues and residual meristematic tissues produce secondary meristems, which then produce secondary tissues. Whereas primary tissues allow for vertical growth, secondary tissues allow for lateral growth: they allow stems and roots to become wider. How might this impact the ability of a plant to grow taller?

In addition to growing wider, secondary growth exchanges the living epidermis for a thick layer of dead, waterproofed cells called cork. The cork and a few other layers of tissue comprise something called the periderm, or perhaps more familiarly called bark. Consider the tradeoffs between having a living exterior with guard cells vs. a thick layer of waterproofed dead cells. How might this impact the ability of the plant to interact with the outer environment? How might this impact the ability of the outer environment to interact with the interior of the plant?

Variations on this type of growth appear in a few places, but the evolution of gymnosperms (conifers and their relatives) is when the more typical secondary growth appears in evolutionary history. As you will see in later labs, the gymnosperms evolved during a period in Earth’s history when inland seas were drying out and plants were migrating further from the water. This group of plants is specialized for growing tall (think Coast redwoods) or living in harsh, low-water environments. As a general rule, monocots do not undergo secondary growth, so this lab will only address eudicots.

The endocrine system is a system of glands called endocrine glands that release chemical messenger molecules into the bloodstream. The messenger molecules of the endocrine system are called endocrine hormones. Other glands of the body, including sweat glands and salivary glands, also secrete substances, but not into the bloodstream. Instead, they secrete them through ducts that carry them to nearby body surfaces. These other glands are not part of the endocrine system. Instead, they are called exocrine glands .

Endocrine hormones act slowly compared with the rapid transmission of electrical messages in the nervous system. Endocrine hormones must travel through the bloodstream to the cells they affect, and this takes time. On the other hand, because endocrine hormones are released into the bloodstream, they travel throughout the body wherever blood flows. As a result, endocrine hormones may affect many cells and have body-wide effects. The effects of endocrine hormones are also longer lasting than the effects of nervous system messages. Endocrine hormones may cause effects that last for days, weeks, or even months.

The Human Digestive System

The process of digestion begins in the mouth with the intake of food. The teeth play an important role in masticating (chewing) or physically breaking food into smaller particles. The enzymes present in saliva also begin to chemically break down food. The food is then swallowed and enters the esophagus—a long tube that connects the mouth to the stomach. Using peristalsis, or wave-like smooth-muscle contractions, the muscles of the esophagus push the food toward the stomach. The stomach contents are extremely acidic, with a pH between 1.5 and 2.5. This acidity kills microorganisms, breaks down food tissues, and activates digestive enzymes. Further breakdown of food takes place in the small intestine where bile produced by the liver, and enzymes produced by the small intestine and the pancreas, continue the process of digestion. The smaller molecules are absorbed into the blood stream through the epithelial cells lining the walls of the small intestine. The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces it is stored until it is excreted through the anus.

Figure 11.4 The components of the human digestive system are shown.

IB Biology - Introduction

When beginning to teach IB Biology it is important to do some long term planning. There would be nothing worse than arriving at the mock exams in year 2 finding 100 hours of IB Biology still to teach. There are some suggestions in the IB guide but everything depends on your teaching situation. In some schools HL and SL are taught together in the same class, in other school they are in separate classes. There may be other constraints regarding shared groups, laboratory space or special events.

This page contains some basic information which will help planning. There is also a page with four suggested Teaching Sequences for the topics which gives outline plans for the two years.

Overall Total Timings. There are 150 hours for SL and 240 hours for HL

The Practical Scheme of Work is also unchanged at: 40 hours for SL and 60 hours for HL

Teaching time for the core topics has increased to 95 hours (from 80 because there is one (15hr) option fewer)

The additional Higher level topics time allocation is 60 hours (from 55 adding 5 hours from the old second option)

Time allocation suggested for the option is now 15 hours for SL and 25 hours for HL (from 30/45 for 2 Options)

From these details above it is clear that there is roughly the same quantity of Biology to cover with both SL and HL students despite the reduction from one to two options.

Note: There are no specific SL options. SL students can study all four options. Each option has extra HL material.

One important area is the practical scheme of work. Section A of paper three will now contain short answer questions about the practical skills students will learn during the course. This ensures that IB Biology remains a practical science course but it will require some careful planning and it could take up a lot of time. To train the students to complete an investigation in just 20 hours of practical activities is quite a challenge.

PSOW - Practical Scheme of Work

Practical scheme of work4060
Practical activities2040
Individual investigation (internal assessment&ndashIA)1010
Group 4 project1010

Six experiments in SL and one in the AHL are listed as practical activities which must be carried out. These skills will be assessed in paper 3 of the examination. There will only be three short questions or data analysis on these practical skills

Monitoring of ventilation at rest and after mild and vigorous exercise

The &ldquoApplications and skills&rdquo section of the syllabus lists 55 additional experiments that students should experience. It is clearly not possible to do each of these in 20 hours total, and so the strategic use of demonstrations and groupwork will be required.

Assessed Individual Investigation (10 hours)

This investigation is the only piece of assessed work required for the 20% internal assessment (IA)

01 Cell biology

This page lists the understandings and skills expected for Topic 1. Helpful for revision.
Detailed revision notes, activities and questions can be found on each of the sub-topic pages.

  • 1.1 Introduction to cells
  • 1.2 Ultrastructure of cells
  • 1.3 Membrane structure
  • 1.4 Membrane transport
  • 1.5 The origin of cells
  • 1.6 Cell division

1.1 Introduction to cells

  • According to cell theory, living organisms are composed of cells.
  • Organisms consisting of only one cell carry out all functions of life in that cell, e.g. Paramecium, Chlorella.
  • Identifying the characteristics of living things (Mr H. Gren - metabolism, response, homeostasis, growth, reproduction, excretion & nutrition).
  • Surface area to volume ratio is important in the limitation of cell size.
  • Multicellular organisms have properties that emerge from the interaction of their cellular components (emergent properties)
  • Specialised tissues can develop by cell differentiation in multicellular organisms.
  • Differentiation involves the expression of some genes and not others in a cell.
  • Stem cells can divide and differentiate along different pathways in embryonic development, which makes stem cells useful for therapeutic uses (e.g. Stargardt's disease).
  • There are ethical concerns about the use of embryo stem cells.
  • Calculate the magnification of an electron microscope image from a scale bar.
  • Calculate specimen size using a scale bar.
  • Calculate specimen size using magnification.

1.2 Ultrastructure of cells

  • The simple structure of Prokaryote cells
  • The compartmentalised structure of Eukaryotic cells.
  • The resolving power of electron microscopes is between 10µm and 1nm whereas light microscopes resolve details between 1mm and 1µm.
  • Explain how the composition of organelles will be different in cells with different functions, e.g. exocrine gland cells (e.g. goblet cells which make mucus and palisade mesophyll cells which do photosynthesis).
  • Application: explain how the structure of prokaryotes allows them to divide by binary fission.

1.3 Membrane structure

  • Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules.
  • Membrane proteins are diverse in terms of structure, position in the membrane and function.
  • Cholesterol is a component of animal cell membranes.
  • Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.
  • Application: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.
  • Can you draw a diagram of the fluid mosaic model?
  • Can you explain how evidence from electron microscopy led to the proposal of the Davson-Danielli model?
  • Can you outline the evidence which led to the falsification of the Davson-Danielli model and support of the Singer-Nicolson model?
  • Application: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.
  • Skill: Drawing of the fluid mosaic model.
  • Skill: Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model.
  • Skill: Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model.

1.4 Membrane function

  • Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.
  • The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells.
  • Know how the structure helps the function of sodium&ndashpotassium pumps for active transport and potassium channels for facilitated diffusion in axons.
  • Understand why tissues (or organs) waiting to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis.
  • Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions (Practical 2).
  • Application: Structure and function of sodium&ndashpotassium pumps for active transport and potassium channels for facilitated diffusion in axons.
  • Application: Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis.
  • Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions (Practical 2).

1.5 The origin of cells and 1.6 Cell division

  • The first cells must have arisen from non-living material.
  • The origin of eukaryotic cells can be explained by the endosymbiotic theory.
  • Mitosis is division of the nucleus into two genetically identical daughter nuclei.
  • Chromosomes condense by supercoiling during mitosis.
  • Cytokinesis occurs after mitosis and is different in plant and animal cells.
  • Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm (including G1, S, G2).
  • Cyclins are involved in the control of the cell cycle.
  • Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.
  • Application: Evidence from Pasteur&rsquos experiments that spontaneous generation of cells and organisms does not now occur on Earth.
  • Application: The correlation between smoking and incidence of cancers.
  • Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph (prophase, metaphase, anaphase and telophase).
  • Skill: Determination of a mitotic index from a micrograph.

Introduction to cells 1.1

Cell theory states that all organisms are made of cells yet the structure of these cells is variable. While this is true in most cases there are some notable exceptions, like skeletal muscle.

Ultrastructure of cells 1.2

Eukaryote cells are larger than prokaryote cells and they have a more compartmentalised structure since endosymbiosis lead to the creation of organelles. Drawing eukaryote and prokaryote cells and recognising organelles is important.

Membrane structure 1.3

The first models of membranes included protein and phospholipids but not in the same structure as we see them today. In this topic the components of cell membranes are investigated and the structure of the membranes as fluid and dynamic structures.

Membrane transport 1.4

The membrane controls what enters and leaves the cell. This includes using diffusion and osmosis. Sometimes the membrane uses integral proteins as channels and pumps, sometimes the membrane surrounds something which needs moving into or out of the cell.

The origin of cells 1.5

Life has evolved from the first cells to all the cells we find in the huge diversity of today's organisms. This topic covers the origins of cells and the cell theory proposed by Pasteur and Schwaan when spontaneous generation of cells was believed.

Cell division 1.6

The control of cell division is just as essential for the survival of multicellular organisms as it is for the reproduction of single celled organisms. This topic covers the movement of chromosomes in the division of eukaryotic cells by mitosis.

11.2: Introduction - Biology

A History of Genetics
(A great site with copies of papers describing key experiments in the development of genetics as a science)

The Genetics Education Center
A great site (from the University of Kansas) with genetics education resources and links to a host of useful web pages.

Classical Genetics
A sensational web page that takes you through the basic principles of genetics (from the Cold Spring Harbor Laboratory in Long Island)

History of Genetics - Timeline
A detailed timeline depicting major events in the history of Genetics.

Chapter 11
Introduction to Genetics

In this chapter, students will read about the principles of genetics and probability that determine how biological traits are inherited. They will also read about the process of meiosis and its importance in genetics.. The links below lead to additional resources to help you with this chapter. These include Hot Links to Web sites related to the topics in this chapter, the Take It to the Net activities referred to in your textbook, a Self-Test you can use to test your knowledge of this chapter, and Teaching Links that instructors may find useful for their students.

Hot Links Take it to the Net
Chapter Self-Test Teaching Links

What are Web Codes?
Web Codes for Chapter 11:
Active Art: Meiosis
Science News: Genetics
SciLinks: Punnett Squares
SciLinks: Mendelian Genetics
SciLinks: Meiosis

Section 11-1: The Work of Gregor Mendel
The principle of dominance states that some alleles are dominant and others are recessive.
When each F1 plant flowers, the two alleles are segregated from each other so that each gamete carries only a single copy of each gene. Therefore, each F1 plant produces two types of gametes—those with the allele for tallness and those with the allele for shortness.

Section 11-2: Probability and Punnett Squares
The principles of probability can be used to predict the outcomes of genetic crosses.

Section 11-3: Exploring Mendelian Genetics
The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes.
Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.

Section 11-4: Meiosis
Meiosis is a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells.

Section 11-5: Linkage and Gene Maps
The chromosomes assort independently individual genes do not.

All About Genetics (with many links to other Genetics sites)

How many chromosomes does a dog have?
How about a cow, a chimp, or a pig?
Click here for the answers.

DP Biology Introduction

This course will teach you a lot about Biology but I also aim to help you learn how to study as well. You will find that as you progress through this course you will encounter exercises which use the same techniques for querying academic content aka knowledge. The main exercises are:

These are tools that you can learn how to use for your own private study and they are useful routines for thinking about any topic that will serve you long after you have forgotten the details of this course.

Before this course introduction I normally give my classes a standard level paper 1. I ask them to answer any questions they can and then make a list of all the unfamiliar words. I then ask them to interrogate a textbook to see if they can answer a further set of unanswered questions.

Then I ask the class to produce a list of vocab they didn't understand in the test. This can than be a springboard into talking about keeping track of vocabulary.

This course introduction combines the following understandings and applications of of topic 1.1:

A2: Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.

U2: Organisms consisting of only one cell carry out all functions of life in that cell.

U4: All organisms are classified into three domains.

U5: The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species.

Imago Education's biology course

There are excellent text books available for this biology course, but students often battle to know how to work with the material in such a way as to master its understanding and application. Frequently they will read through the text book, and perhaps answer some of the questions, believing that this is all that is required. What is really needed, though, is a comprehensive, systematic, structured set of learning activities that will the student to a mastery of the subject. It is Imago Education's aim to provide such a set of learning activities, divided into manageable lessons, that will guide the student through the learning process and enable him/her to prepare thoroughly for the final exam.

We will be using Cambridge IG Biology Coursebook by Mary Jones and Geoff Jones, third edition (Cambridge University Press, 2014, ISBN:978-1-107-61479-6 as well as Cambridge IG Biology Workbook, by Mary Jones and Geoff Jones, third edition (Cambridge University Press, 2014, ISBN: 978-1-107-61493-2. Note the one is a coursebook which has the main text and the other is the workbook which has important exercises for the students to work through. Both these books are endorsed by Cambridge International and therefore meets their requirements for this course. The text book is well written and is particularly suitable for the private candidate studying on their own.

While this course will point out the practical skills which need to be learned, it is by it's nature limited in providing the student with the skills required for the practical exam. Since at IG level, students can write Paper 6 (alternative to practical) instead of Paper 5 (practical test), this is not such a problem. The student should however, where possible, and under the guidance of an adult attempt as many of the practical activities as possible.

The menu at the left hand side provides a table of contents for all the lessons in this course. To get a feel for how the course works, please look at the free lessons available (indicated with *).

Sex and Death

Is the history of life a series of accidents or a drama scripted by selfish genes? Is there an "essential" human nature, determined at birth or in a distant evolutionary past? What should we conserve—species, ecosystems, or something else?

Informed answers to questions like these, critical to our understanding of ourselves and the world around us, require both a knowledge of biology and a philosophical framework within which to make sense of its findings. In this accessible introduction to philosophy of biology, Kim Sterelny and Paul E. Griffiths present both the science and the philosophical context necessary for a critical understanding of the most exciting debates shaping biology today. The authors, both of whom have published extensively in this field, describe the range of competing views—including their own—on these fascinating topics.

With its clear explanations of both biological and philosophical concepts, Sex and Death will appeal not only to undergraduates, but also to the many general readers eager to think critically about the science of life.

Part I - Theory Really Matters: Philosophy of Biology and Social Issues
1.1. The Science of Life Itself
1.2. Is There an Essential Human Nature?
1.3. Is Genuine Altruism Possible?
1.4. Are Human Beings Programmed by Their Genes?
1.5. Biology and the Pre-emption of Social Science
1.6. What Should Conservationists Conserve?
2. The Received View of Evolution
2.1. The Diversity of Life
2.2. Evolution and Natural Selection
2.3. The Received View and Its Challenges
Part II - Genes, Molecules, and Organisms
3. The Gene’s Eye View of Evolution
3.1. Replicators and Interactors
3.2. The Special Status of Replicators
3.3. The Bookkeeping Argument
3.4. The Extended Phenotype
4. The Organisim Strikes Back
4.1. What Is a Gene?
4.2. Genes Are Active Germ Line Replicators
4.3. Genes Are Difference Makers
5. The Developmental Systems Alternative
5.1. Gene Selectionism and Development
5.2. Epigenetic Inheritance and Beyond
5.3. The Interactionist Consensus
5.4. Information in Development
5.5. Other Grounds for Privileging Genes
5.6. Developmental Systems and Extended Replicators
5.7. One True Story?
6. Mendel and Molecules
6.1. How Theories Relate: Displacement, Incorporation, and Integration
6.2. What Is Mendelian Genetics?
6.3. Molecular Genetics: Transcription and Translation
6.4. Gene Regulation
6.5. Are Genes Protein Makers?
7. Reduction: For and Against
7.1. The Antireductionist Consensus
7.2. Reduction by Degrees?
7.3. Are Genes DNA Sequences Plus Contexts?
7.4. The Reductionist Anticonsensus
Part III - Organisms, Groups, and Species
8. Organisms, Groups, and Superorganisms
8.1. Interactors
8.2. The Challenge of Altruism
8.3. Group Selection: Take 1
8.4. Group Selection: Take 2
8.5. Population-Structured Evolution
8.6. Organisms and Superorganisms
9. Species
9.1. Are Species Real?
9.2. The Nature of Species
9.3. The One True Tree of Life
9.4. Species Selection
Part IV - Evolutionary Explanations
10. Adaptation, Perfection, Function
10.1. Adaptation
10.2. Function
10.3. The Attack on Adaptationism
10.4. What Is Adaptationism?
10.5. Structuralism and the Bauplan
10.6. Optimality and Falsifiability
10.7. Adaptation and the Comparative Method
11. Adaptation, Ecology, and the Environment
11.1. The Received View in Ecology
11.2. History and Theory in Ecology
11.3. The Balance of Nature
11.4. Niches and Organisms
11.5. Reconstructing Niches
11.6. Unfinished Business
12. Life on Earth: The Big Picture
12.1. The Arrow of Time and the Ladder of Progress
12.2. Gould’s Challenge
12.3. What Is Disparity?
12.4. Contingency and Its Consequences
12.5. Mass Extinction and the History of Life
12.6. Conclusions
Part V - Evolution and Human Nature
13. From Sociobiology to Evolutionary Psychology
13.1. 1975 and All That
13.2. The Wilson Program
13.3. From Darwinian Behaviorism to Darwinian Psychology
13.4. Evolutionary Psychology and Its Promise
13.5. Evolutionary Psychology and Its Problems
13.6. Memes and Cultural Evolution
14. A Case Study: Evolutionary Theories of Emotion
14.1. Darwin on the Emotions
14.2. Sociobiology and Evolutionary Psychology on the Emotions
14.3. The Modular Emotions
14.4. Beyond the Modular Emotions
14.5. Emotion, Evolution, and Evolved Psychology
Part VI - Concluding Thoughts
15. What Is Life?
15.1. Defining Life
15.2. Universal Biology
15.3. Simulation and Emergence
Final Thoughts

11.2: Introduction - Biology

Figure 1. The leaf chameleon (Brookesia micra) was discovered in northern Madagascar in 2012. At just over one inch long, it is the smallest known chameleon. (credit: modification of work by Frank Glaw, et al., PLOS)

Animal evolution began in the ocean over 600 million years ago with tiny creatures that probably do not resemble any living organism today. Since then, animals have evolved into a highly diverse kingdom. Although over one million extant (currently living) species of animals have been identified, scientists are continually discovering more species as they explore ecosystems around the world. The number of extant species is estimated to be between 3 and 30 million.

But what is an animal? While we can easily identify dogs, birds, fish, spiders, and worms as animals, other organisms, such as corals and sponges, are not as easy to classify. Animals vary in complexity—from sea sponges to crickets to chimpanzees—and scientists are faced with the difficult task of classifying them within a unified system. They must identify traits that are common to all animals as well as traits that can be used to distinguish among related groups of animals. The animal classification system characterizes animals based on their anatomy, morphology, evolutionary history, features of embryological development, and genetic makeup. This classification scheme is constantly developing as new information about species arises. Understanding and classifying the great variety of living species help us better understand how to conserve the diversity of life on earth.

Watch the video: Introduction to plant ecology module - Ecological filters and succession (November 2021).